delivered the opinion of the Court.

In June 1972, the Rosebud Sioux Tribe sued in the United States District Court for the District of South Dakota to obtain a declaratory judgment that the original boundaries of their reservation, as defined in the Act of March 2, 1889, 25 Stat. 888, had not been diminished by three subsequent Acts of Congress passed in 1904, 1907, and 1910 respectively.1 The District Court, noting that “[f]rom the time these acts were passed, these [four] counties have been treated as outside the Rosebud Sioux Reservation by the settlers, their descendants, the State of South Dakota and the federal courts,” 375 F. Supp. 1065, 1084, denied relief. It concluded that Congress had intended to diminish the Reservation so as to exclude the four counties in South Dakota affected by the 1904, the 1907, and the 1910 Acts. The United States Court of Appeals for the Eighth Circuit, in a careful and comprehensive opinion, affirmed the judgment of the District Court. 521 F. 2d 87. We granted certiorari, 425 U. S. 989, to review this determination in the light of our recent decisions in DeCoteau v. District County Court, 420 U. S. 425 (1975), and Mattz v. Arnett, 412 U. S. 481 (1973). Since we conclude that the three Acts *586of Congress in question satisfy the requirement that “[a] congressional determination to terminate [an Indian reservation] must be expressed on the face of the Act or be clear from the surrounding circumstances and legislative history,” Mattz v. Arnett, supra, at 505, we affirm the judgment of the Court of Appeals.

I

When established, the Rosebud Indian Reservation contained somewhat over 3.2 million acres, and covered all or a portion of what later became five counties in South Dakota: Gregory, Tripp, Lyman, Mellette, and Todd. The three Acts we are asked to construe successively disposed of all unallotted lands in Gregory County (1904 Act), in Tripp and Lyman Counties (1907 Act), and in Mellette County (1910 Act). Only Todd County remains unaffected by these post-1889 enactments. The contention of the Rosebud Sioux Tribe is that these Acts, while opening up the unallotted land outside of Todd County to non-Indian settlement, did not thereby change the Reservation boundaries, which continued to encompass these five counties.

In determining whether or not the 1889 Reservation boundaries were subsequently diminished by congressional enactments, we are guided by well-established legal principles. The underlying premise is that congressional intent will control. DeCoteau v. District County Court, supra, at 444, 449; United States v. Celestine, 215 U. S. 278, 285 (1909). In determining this intent, we are cautioned to follow “the general rule that ‘[d]oubtful expressions are to be resolved in favor of the weak and defenseless people who are the wards of the nation, dependent upon its protection and good faith.' ” McClanahan v. Arizona State Tax Comm’n, 411 U. S. 164, 174 (1973), quoting Carpenter v. Shaw, 280 U. S. 363, 367 (1930); see also Mattz v. Arnett, supra, at 505. The mere fact that a reservation has been opened to settlement does not necessarily mean that the opened area has lost its reservation *587status. Mattz v. Arnett, supra; see also Seymour v. Superintendent, 368 U. S. 351 (1962). But the “general rule” does not command a determination that reservation status survives in the face of congressionally manifested intent to the contrary. DeCoteau v. District County Court, supra. In all cases, “the face of the Act,” the “surrounding circumstances,” and the “legislative history,” are to be examined with an eye toward determining what congressional intent was. Mattz v. Arnett, supra, at 505.

Applying these principles to the facts of this case, we conclude that the Acts of 1904, 1907, and 1910 did clearly evidence congressional intent to diminish the boundaries of the Rosebud Sioux Reservation. The parties agree that an amendment to the 1889 Treaty, which provided for a fixed-sum payment and which was approved by three-fourths of the Rosebud Sioux Tribe’s adult males in 1901, would have resulted in the diminution of the Rosebud Reservation boundaries. Congress did not, however, approve the 1901 amendment to the Treaty which the Tribe had ratified. The Tribe contends that, lacking tribal ratification and a fixed-sum provision, the later Acts were ineffectual to accomplish this same result. In the Tribe’s view, the absence of these two factors vitally distinguishes the Acts in question from the otherwise similar Act examined in DeCoteau v. District County Court, supra. Because of the reasons hereafter set forth in greater detail, we conclude that, although the Acts of 1904, 1907, and 1910 were unilateral Acts of Congress without the consent of three-quarters of the members of the tribe required by the original Treaty,2 that fact does not have any direct bearing on the question of whether Congress by these later Acts did intend to diminish the Reservation boundaries. By the time of *588the first of these Acts, in 1904, Congress was aware of the decision of this Court in Lone Wolf v. Hitchcock, 187 U. S. 553 (1903), which held that Congress possessed the authority to abrogate unilaterally the provisions of an Indian treaty. We also conclude that the changed method of payment is not conclusive with respect to congressional intent. Although the later Acts of Congress made less secure provisions for payment to the Tribe for the lands in question than did the 1901 Treaty, their language with respect to the reservation status of the opened lands was identical with or derivative from the language used in that proposed amendment.3 The language was also substantially equivalent to that used in the executed agreement involved in DeCoteau. We agree with the Court of Appeals and the District Court that this language not only opened the land for settlement, but diminished the boundaries of the Reservation pro tanto.4

*589II

The Rosebud Sioux are one of the tribes of Indians of the Sioux Nation. The Treaty of April 29, 1868, 15 Stat. 635, set aside all the land in South Dakota west of the Missouri River as the Great Sioux Reservation, consisting of some 25 million acres. Article 12 of the Treaty provided that no subsequent treaty for the cession of any part of the reservation would be valid without the written consent of three-fourths of the adult male Indians on the reservation. Despite this provision, in 1877 approximately 7.5 million acres, consisting of the Black Hills portion of the Great Sioux Reservation, were removed from the Reservation by the Act of February 28, 1877, 19 Stat. 254. See Sioux Tribe of Indians v. United States, 97 Ct. Cl. 613 (1942), cert. denied, 318 U. S. 789 (1943). Of the remaining Reservation, approximately one-half was “restored to the public domain” under the Act of March 2, 1889, 25 Stat. 896, § 21,5 while six separate Reservations were carved out of the remainder, §§ 1-6. Section 2 set apart the Rosebud Reservation, encompassing what were later organized as three full counties (Todd, Mellette, and Tripp), a major portion of Gregory County, and a small portion of Lyman.6 This Reservation, as originally delimited, contained over 3.2 million acres.

*590Around the turn of the century, the “familiar forces” to which we referred in DeCoteau v. District County Court, led to demands to open up the Reservation.7 A provision in the Indian Department Appropriation Act, Mar. 3, 1901, 31 Stat. 1077, provided:

“[T]he Secretary of the Interior be, and he is hereby, authorized, in his discretion, to negotiate, through any United States Indian inspector, agreements with any Indians for the cession to the United States of portions of their respective reservations or surplus unallotted lands, any agreements thus negotiated to be subject to subsequent ratification by Congress.”

Shortly thereafter Inspector James McLaughlin was instructed by the Commissioner of Indian Affairs to begin “negotiations with the Indians of the Rosebud reservation, in South Dakota, for the cession of the unallotted eastern portion of their reserve.” Letter dated Mar. 19, 1901, from W. A. Jones, Commissioner, Office of Indian Affairs, Department of Interior. Following meetings with members of the Tribe during the spring and summer of 1901, Inspector McLaughlin obtained the written consent of three-fourths of the *591male Indian adults to the cession of some 416,000 acres of unallotted land in Gregory County for the sum of $1,040,000, subject to congressional ratification.8 The negotiated Agreement, however, was never ratified,9 “because of the fact that it provided that the Government should pay for the lands outright . . . ." 38 Cong. Rec. 1423 (1904) (remarks of Rep. Burke) .10

What is important for our purposes is the undisputed fact that the 1901 Agreement, had it been ratified by Congress, would have disestablished that portion of the Rosebud Reservation which lay in Gregory County. Inspector McLaughlin explained to the Tribe that “[t]he cession of Gregory County” by ratification of the Agreement “will leave your reservation a compact, and almost square tract, and would leave your *592reservation about the size and area of Pine Ridge Reservation.” 11 It is conceded that his description was correct; the effect and intent of the 1901 Agreement, if ratified, would have been to change the Reservation boundaries. As we noted in DeCoteau v. District County Court, 420 U. S., at 445, in construing virtually identical language: “The Agreement’s language . . . was precisely suited to this purpose [of disestablishment].” In this Agreement, therefore, we have—unlike the situation in Mattz v. Arnett, 412 U. S. 481 (1973)—an unmistakable baseline purpose of disestablishment.

An examination of the legislative processes which resulted in the 1904 Act convinces us, as it did the lower courts, that this purpose was carried forth and enacted. Because of the history of the 1901 Agreement, the 1904 Act cannot, and should not, be read as if it were the first time Congress had addressed itself to the diminution of the Rosebud Reservation.

In 1903, new bills were introduced, and subsequently reported from committee in both chambers of Congress, which proposed “to adopt a new policy in acquiring lands from the Indians [by] provid[ing] that the lands shall be disposed of to settlers . . ., and to be paid for by the settlers, and the money to be paid to the Indians only as it is received . . . from the settlers.” 12 The Senate bill, S. 7390, passed the Senate in February, 36 Cong. Rec. 2748 (1903), but the 57th Congress expired before the House could give it consideration. In line with the changes in S. 7390, which related to the method of payment, Inspector McLaughlin was subsequently instructed to go to the Rosebud Reservation to negotiate a new *593agreement.13 He explained to the Rosebud Tribe: “I am here to enter into an agreement which is similar to that of two years ago, except as to the manner of payment . . . . You will still have as large a reservation as Pine Ridge after this is cut off.” 14

Inspector McLaughlin failed to get three-fourths of the adult male Indians to consent to this new method of payment, although he did obtain the consent of a majority, provided that the price to homesteaders be raised from $2.50 to $2.75 per acre. Agreement of Aug. 10, 1903.15 How*594ever, as Inspector McLaughlin had explained to the Tribe,16 Congress understood that it was not bound by the three-fourths-consent requirement of the 1868 Treaty with the Sioux Nation. In Lone Wolf v. Hitchcock, 187 U. S., at 566, 568, this Court, dealing with the validity of a cession of tribal lands enacted in contravention of a treaty requiring three-fourths Indian consent, held:

“The power exists to abrogate the provisions of an Indian treaty, though presumably such power will be exercised only when circumstances arise which will not only justify the government in disregarding the stipulations of the treaty, but may demand, in the interest of the country and the Indians themselves, that it should do so. When, therefore, treaties were entered into between the United States and a tribe of Indians it was never doubted that the power to abrogate existed in Congress . . . .

“. . . In any event, as Congress possessed full power in the matter, the judiciary cannot question or inquire into the motives which prompted the enactment of this legislation.”

Although Inspector McLaughlin failed to garner the signatures of three-quarters of the Indians in consent of the proposed changes, Congress understandably relied on this holding as authorizing it to diminish unilaterally the Reservation boundaries.

In examining congressional intent, there is no indication *595that Congress intended to change anything other than the form of, and responsibility for, payment. In recommending ratification of the 1901 Agreement, as modified, the accompanying House Report stated:

“The purpose of this bill is to ratify and amend an agreement made with the Rosebud Indians in South Dakota by Inspector James McLaughlin, dated September 14, 1901, providing for the cession to the United States of the unallotted portion of their lands in Gregory County, S. Dak., and opening the same to settlement and entry under the homestead and town-site laws.

“There is no question but what the Indians have no use for the land that is proposed to be ceded by this bill; that the tract is only a very small portion of the Rosebud Reservation, and is really only a corner of the reservation, which will be left compact and in a square tract and a reservation about equal in size to the Pine Ridge Reservation, in South Dakota.”17

On the floor of the House, Congressman Burke, the 1904 Act’s sponsor, in discussing the changes in the Agreement since *5961901, made clear that the new bill was concerned only with the responsibility for payment, 38 Cong. Rec. 1423 (1904):

“Mr. BURKE. . . . In 1901 a treaty was entered into with the Rosebud Indians on the part of the United States, by which the Indians agreed to sell to the Government this land for $2.50 per acre. That treaty was transmitted to Congress, and because of the fact that it provided that the Government should pay for the lands outright and then take the chance of the Treasury being reimbursed by disposing of the lands to settlers, it never got further than through the Committee on Indian Affairs, which unanimously reported it favorably. It was never given consideration in the House.

“Toward the concluding days of the last session of Congress a new bill was prepared, substantially as this bill now provides, and that bill provided that the lands should be ceded by the Indians to the Government, disposed of to settlers under the provisions of the homestead law, the price to be fixed at $2.50 an acre, as was provided in the original treaty. . . . This bill is substantially the same as the bill which I have just referred to . . . ."

The bill itself, as introduced and passed by both Houses, incorporated the entire text of the 1903 Agreement, which itself followed the 1901 Agreement except that: (1) the Indians were not guaranteed any consideration for the land except with respect to the 16th and 36th sections (school sections), but were to be paid only as the lands were actually sold to settlers; (2) the United States did not guarantee to find purchasers but agreed only to “act as trustee for said Indians to dispose of said lands.” 18 In particular, the 1904 *597Act incorporated verbatim the language of immediate cession of the 1901 Agreement:

“The said Indians belonging on the Rosebud Reservation, South Dakota, for the consideration hereinafter named, do hereby cede, surrender, grant, and convey to the United States all their claim, right, title, and interest in and to all that part of the Rosebud Indian Reservation now remaining unallotted, situated within the boundaries of Gregory County . . . ." 33 Stat. 256.

As in DeCoteau v. District County Court, 420 U. S., at 445, this language is “precisely suited” to disestablishment.

Petitioner, however, objects that a “cession” requires bilateral consent, and the failure of Inspector McLaughlin to gain the approval of three-quarters of the male adult Indians vitiates any “cession.” As a matter of strict English usage, petitioner is undoubtedly correct: “cession” refers to a voluntary surrender of territory or jurisdiction, rather than a withdrawal of such jurisdiction by the authority of a superior sovereign. But as Mr. Justice (then Judge) Holmes commented, we are not free to say to Congress: “We see what you are driving at, but you have not said it, and therefore we shall go on as before.” Johnson v. United States, 163 F. 30, 32 (CA1 1908). Congress was simply repeating verbatim language from a bill ratifying the 1901 Agreement, which had made the proper use of the word “cession” because the Agreement had been approved by the Tribe. The use of the word “cession” in the 1904 Act, which was not consented to by the required extraordinary majority of the Tribe, does-not make the meaning of the Act ambiguous as between diminution of the Reservation boundaries on the one hand, and merely opening up designated lands for settlement by non-Indians, on the other. The word is technically misused, but the meaning is quite clear. It was *598intended to accomplish, in 1904, precisely what it was intended to accomplish in 1901. Congress was under no misapprehension that the required portion of the Tribe had in fact approved the treaty. It knew that while a majority of the Tribe had approved it, the required extraordinary majority had not; but it had determined nonetheless to go ahead and accomplish the same result unilaterally as the Agreement would have accomplished bilaterally.19

The “bill provided that the lands should be ceded by the Indians to the Government. . . ." 38 Cong. Rec. 1423 (1904) (remarks of Rep. Burke). It is clear that Congress was relying on Lone Wolf v. Hitchcock, 187 U. S. 553 (1903), in making this unilateral declaration. There is nothing in the changed method of payment, or the failure to obtain a three-quarters vote from the Indians, which indicates that the clear intent of the 1901 Agreement to diminish the Reservation boundaries had changed between 1901 and 1904.20 The Tribe, moreover, was eventually paid for the land, supra, at 588 n. 3.

*599This implied continuity in purpose from 1901 to 1904 does not, however, stand alone in indicating congressional intent. Section 4 of the 1904 Act, 33 Stat. 258, provides, in pertinent part:

“[S]ections sixteen and thirty-six of the lands hereby acquired in each township shall not be subject to entry, but shall be reserved for the use of the common schools and paid for by the United States at two dollars and fifty cents per acre, and the same are hereby granted to the State of South Dakota for such purpose . . . ."

When North and South Dakota were admitted into the Union, § 10 of the admitting Act, Act of Feb. 22, 1889, 25 Stat. 679, provided, in pertinent part:

“[U]pon the admission of each of said States into the Union sections numbered sixteen and thirty-six in every township of said proposed States . . . are hereby granted to said States for the support of common schools . . . : Provided, That the sixteenth and thirty-sixth sections embraced in permanent reservations for national pur*600poses shall not, at any time, be subject to the grants . . . of this act, nor shall any land embraced in Indian, military, or other reservations of any character be subject to the grants ... of this act until the reservation shall have been extinguished and such lands be restored to, and become a part of, the public domain.”

The language of § 10 is mandatory: “nor shall” the 16th and 36th sections of lands within Indian reservations “be subject to the grants . . . until the reservation shall have been extinguished . . . .” While Congress would have had the power to establish other grants, cf. 43 U. S. C. § 856, the legislative history, in this case, demonstrates that Congress “included the provision to implement the grant in the enabling act and for no other reason.” 521 F. 2d, at 101.21 Both the House and Senate Reports explicitly noted that the “school sections” provision of what became the 1904 Act “is in conformity with the guarantee given to the State of South Dakota by Congress in the enabling act. . . .” 22 Congress, therefore, clearly thought that it was acting pursuant to § 10 of the Act of February 22, 1889, and not sub silentio adding an additional grant for *601school lands located within a continuing reservation.23 The far more natural construction, then, is to read a congressional intent to disestablish Gregory County from the Rosebud Reservation, thereby making the sections available for disposition to the State of South Dakota for “school sections” under § 10 of the Act of February 22, 1889.24

*602That it was clearly understood, at least by the Executive Branch, that the 1904 Act, like the 1901 Agreement, contemplated a diminution of the Reservation, is apparent from the Rosebud Proclamation of May 13, 1904, 33 Stat. 2354. In accordance with the requirement of § 2 of the 1904 Act that the land would “be disposed of under the general provisions of the homestead and town-site laws of the United States, and shall be opened to settlement and entry,” the Proclamation stated, in pertinent part:

“Whereas by an agreement between the Sioux tribe of Indians on the Rosebud Reservation, in the State of South Dakota, on the one part, and James McLaughlin, a United States Indian Inspector, on the other part, amended and ratified by act of Congress . . . the said Indian tribe ceded, conveyed, transferred, relinquished, and surrendered, forever and absolutely, without any reservation whatsoever, expressed or implied, unto the United States of America, all their claim, title, and interest of every kind and character in and to the unallotted lands embraced in the following described tract of country now in the State of South Dakota, . . .

“NOW, THEREFORE, I, THEODORE ROOSEVELT, President of the United States of America, by virtue of the power vested in me by law, do hereby declare and make known that all of the lands so as aforesaid ceded by the Sioux tribe of Indians of the Rosebud Reservation . . . will, on the eighth day of August, 1904, at 9 o’clock a. m., in the manner herein prescribed and not otherwise, be opened to entry and settlement and to disposition under the general provisions of the homestead and townsite laws of the United States.” (Emphasis supplied.)

The opening portion of the Proclamation is an unambiguous, contemporaneous, statement, by the Nation’s Chief Executive, *603of a perceived disestablishment of Gregory County. It reflects, we believe, the clear import of the congressional action in the 1904 Act.

In sum, an examination of the process leading up to the enactment of the 1904 Act, as well as the language and legislative history, leads us, as it led the Court of Appeals and the District Court, to the firm conclusion that congressional intent was to exclude Gregory County from the Rosebud Reservation.25

Although the subsequent “jurisdictional history,” DeCoteau v. District County Court, 420 U. S., at 442, is not entirely clear, the single most salient fact is the unquestioned actual assumption of state jurisdiction over the unallotted lands in Gregory County since the passage of the 1904 Act, see 375 F. Supp., at 1084; Amended Complaint ¶ 21.26 Since state *604jurisdiction over the area within a reservation's boundaries is quite limited, 18 U. S. C. § 1151; McClanahan v. Arizona State Tax Comm’n, 411 U. S. 164 (1973) ; Williams v. Lee, 358 U. S. 217 (1959); Worcester v. Georgia, 6 Pet. 515 (1832), the fact that neither Congress nor the Department of Indian Affairs has sought to exercise its authority over this area, or to challenge the State's exercise of authority is a factor entitled to weight as a part of the “jurisdictional history.” 27 The long*605standing assumption of jurisdiction by the State over an area that is over 90% non-Indian, both in population and in land use, not only demonstrates the parties' understanding of the meaning of the Act, but has created justifiable expectations which should not be upset by so strained a reading of the Acts of Congress as petitioner urges.28 We are simply unable to conclude that the intent of the 1904 Act was other than to disestablish.

III

Having determined that the 1904 Act carried forth the intent to disestablish which was unquestionably manifested in the 1901 Agreement, our examination of the 1907 and the *6061910 Acts is made easier. None of the parties really disputes that the intent of the three Acts was the same.29 Because the later Acts do vary in some respects, however, we shall explain briefly why we find a continuity of intent through the 1907 and the 1910 Acts.30

The “familiar forces" at work pressing for the opening of Indian lands did not cease with the cession of Gregory County. By late 1906, Congressman Burke was preparing a bill dealing with the “sale of that part of the reservation located in Tripp County.” 31 Inspector McLaughlin was instructed to proceed to the Rosebud Reservation to negotiate an agreement for land in Tripp County which when “ceded should be disposed of under the general provisions of the homestead and townsite laws of the United States,” and he was given suggested terms, “similar to those in the disposal *607of the ceded lands in Gregory County 32 Inspector McLaughlin’s negotiations produced virtually the same result as in 1904. A 1907 Agreement, signed by a majority, but not by three-fourths, of the adult male Indians, provided that the Indians “do hereby cede, grant, and relinquish to the United States all claim, right, title, and interest in and to all that part of the Rosebud Indian Reservation [in Tripp and Lyman Counties], except such portions thereof as have been, or may hereafter be, allotted to Indians.” 33 The Secretary of the Interior recommended that Congress ratify the Agreement, Letter from E. A. Hitchcock, supra, n. 33, and the Senate Committee on Indian Affairs reported a ratification bill out, S. Rep. No. 6831, 59th Cong., 2d Sess. (1907). By this time, however, the House had already passed a second bill introduced by Congressman Burke which did not incorporate the Agreement, 41 Cong. Rec. 3103-3105 (1907) (H. R. 24987), although it did substantially incorporate the terms of the Agreement, as noted by Congressman Burke, id., at 3104:

“The bill is substantially in accordance with an agreement which has just been made with the Indians, signed by [a majority]. . . . It is along the line of the bill which passed in the Fifty-eighth Congress for the sale of that portion of this same reservation that is located in Gregory County.

*608". . . They will have left, after this land is disposed of, a reservation that is substantially 50 miles square . . . .” 34

The operative language of the bill, subsequently passed by the Senate without debate, and enacted into law, 34 Stat. 1230, provided:

“[T]he Secretary of the Interior be, and he is hereby, authorized and directed, as hereinafter provided, to sell or dispose of all that portion of the Rosebud Indian Reservation in South Dakota [in Tripp and Lyman Counties], except such portions thereof as have been, or may hereafter be, allotted to Indians . . . .”

As the parties recognize, the substance of the 1907 Act is identical to the 1904 Act. Section 2 provides for the disposition of lands under the “general provisions of the homestead and town-site laws,” while § 3 specifies land purchase prices, with the proviso that “any lands remaining unsold after the said lands have been opened to entry for seven years may be sold to the highest bidder for cash, without regard to the above minimum limit of price.” 35 Section 6 provides for the purchase by the United States of sections 16 and 36 of the lands in each township and their transfer to South Dakota for “the use of the common schools.” 36 Sections 5 and 7 provide that the United States is to act as trustee for the Indians to dispose of the lands and to collect and dispense the proceeds.37

In virtually all respects, then, except for the operative language in § 1 replacing the Agreement language, the 1907 *609Act is a functional twin of the 1904 Act. And, as the legislative comments make clear, supra, at 607-608, the change in § 1 language was not intended to modify or change the purposes or operation of the 1904 Act.38 We agree with the Court of Appeals’ conclusion, 521 F. 2d, at 104:

“Nothing in the language of the 1907 Act or in the surrounding circumstances and legislative history indicates a change in that congressional determination to alter the reservation boundaries which we have found in the 1904 Act.”

The 1907 Act, like the 1904 Act which preceded, it, disestablished the land in Tripp and Lyman Counties from the Rosebud Reservation.

The pressures for more land had not yet expended themselves with the passage of the 1907 Act. In late 1908, Senator Gamble submitted a new bill authorizing the sale and disposition of a portion of the surplus and unallotted lands in Mellette County and in a strip located in the eastern part of Todd County, S. 7379, 43 Cong. Rec. 65 (1908). The accompanying Senate Report noted, in proposing the opening to settlement of an area comprising about 900,000 acres, that “[t]he present area of the Rosebud Indian Reservation aggregates 1,800,000 acres.” S. Rep. No. 887, 60th Cong., 2d Sess., 1 (1909) (emphasis supplied).39 The school-sections *610provision was again included in the bill, “to be paid for by the Government in conformity with the provisions of the act admitting the State of South Dakota into the Union.” Id., at 2.40 Senator Gamble was unable to have the Senate consider the bill before the term of Congress expired, and Inspector McLaughlin was once again dispatched to conduct negotiations with the Rosebud Tribe concerning the Gamble bill.41 This time, he did not seek to negotiate an agreement with the Indians, but reported back to the Secretary of the Interior the “practically unanimous” concurrence of the Indians “in the opening of the northern strip, provided the two *611tiers of townships in the eastern part of Meyer [sic] County remain a part of the diminished reservation.”42

New bills were introduced similar in purpose to the original Gamble bill.43 The Secretary of the Interior recommended to Congress that the bill open only Mellette County, and not the eastern part of Todd County, and that the bill also include a provision subjecting the land to be opened “for a period of twenty-five years to all the laws of the United States prohibiting the introduction of intoxicants into the Indian country.” 44 These changes were made in S. 183, see S. Rep. No. 68, 61st Cong., 2d Sess. (1910). The Report noted, id., at 2-4:

“The present area of the Rosebud Indian Reservation aggregates about 1,800,000 acres. The lands proposed to be opened to settlement under the provisions of this bill embrace an area of about 830,000 acres. . . .

“. . . . It also provides that the Secretary of the Interior, in his discretion, may permit Indians who have allotments within the area proposed to be opened to relinquish such allotments and to receive in lieu thereof allotments anywhere within the reservation proposed to be diminished.

“Sections 16 and 36 of the lands in each township are not to be disposed of, but are reserved for the use of the common schools of the State, and these lands are to be paid for by the Government in conformity with the pro*612visions of the act admitting the State of South Dakota into the Union. . . .

“Although Congress has full power to enact legislation of this character without the consent of the Indians, it was felt the Indians should be fully advised as to the provisions of the pending measure and their views should be asked in regard thereto.”

The bill was passed by the Senate on January 17, 1910, 45 Cong. Rec. 1065-1066, 1075 (1910), and the House Committee on Indian Affairs decided to adopt the Senate bill, its Report noting:

“The Rosebud Indian Reservation when set aside as a separate reservation under the Sioux act of 1889 contained something over 3,000,000 acres of land. [Then follows a description of the 1904 Act and the 1907 Act, observing that the 1907 Act was “substantially in the same form as the bill now under consideration . . . .”]

“The area comprised in the present bill is about 800,000 acres . . . . There will still be left a reservation containing about 1,000,000 acres, and as the Indians have all been allotted there is no occasion for continuing a reservation larger than it will be when Mellette County is disposed of.”45

The bill then passed the House with amendments, id., at 5473, and, after conference to reconcile differences in the House and Senate bills not material here, the bill became law on May 30, 1910.46

The 1910 Act is substantially similar to the 1907 Act, and *613uses identical operative language authorizing and directing the Secretary of the Interior “to sell and dispose of all that portion of the Rosebud Indian Reservation [in present day Mellette County] except such portions thereof as have been or may be hereafter allotted to Indians . . . ." 36 Stat. 448. Because of the substantive similarity of the Acts, no useful purpose would be served in recounting the similar provisions contained in the 1910 Act. Two new provisions, however, do warrant mention. The first is a proviso in § 1, stating:

“[A]ny Indians to whom allotments have been made on the tract to be ceded may, in case they elect to do so before said lands are offered for sale, relinquish same and select allotments in lieu thereof on the diminished reservation.”

This proviso, on its face, is a strong indication of the continuing intent to disestablish the affected areas, first manifested in the 1901 Agreement. The second is the provision in § 10 of the 1910 Act, included at the suggestion of the Secretary of the Interior, subjecting the opened land “for a period of twenty-five years to all the laws of the United States prohibiting the introduction of intoxicants into the Indian country.” As there existed, in 1910, an outstanding prohibition against the introduction of intoxicants into “Indian country,” see Act of July 23, 1892, 27 Stat. 260, the most reasonable inference from the inclusion of this provision is that Congress was aware that the opened, unallotted areas would henceforth not be “Indian country,” because not in the Reservation.47

*614These added provisions, as well as the clear legislative history of the 1910 Act, reflect strongly the continued intent to diminish the Reservation boundaries. We conclude that *615the 1910 Act continued the policies of the prior two Acts, and Mellette County was thereby detached from the Reservation.

IV

The intent of Congress in the 1904, the 1907, and the 1910 Acts was to change the boundaries of the original 1889 Rosebud Reservation. Much has changed since then, and if Congress had it to do over again it might well have chosen a different course. But, as we observed in DeCoteau v. District County Court, 420 U. S., at 449: “[O]ur task here is a narrow one. . . . [W]e cannot remake history.” 48 Affirmed.

with whom Mr. Justice Brennan and Mr. Justice Stewart join, dissenting.

The Court holds today that in 1904, 1907, and 1910, Congress broke solemn promises it had made to the Rosebud *616Sioux Tribe and took from them, without any guarantee of compensation, three-quarters of their reservation. Although it was suggested at argument, Tr. of Oral Arg. 18-20, that the only consequence of such a holding would be to preclude the Tribe from continuing to exercise the jurisdiction granted to it by its approved constitution and bylaws,1 in fact much more is at stake. This case involves not just the rights of the Tribe, but also the rights of approximately 2,000 Indians living in the disputed area, and the right of the United States to continue to administer the disputed area as part of the Rosebud Reservation.2 See Part IV, infra. In addition, the *617ramifications of today’s decision may extend to a large number of other reservations throughout the Nation. See ibid. I therefore feel constrained to explain at length why the decision is, in my view, wholly unjustifiable.

Until today, the effect on reservation boundaries of Acts disposing of surplus reservation land was well settled. The general rule, entitled to “the broadest possible scope,” is that in interpreting these Acts “legal ambiguities are resolved to the benefit of the Indians.” DeCoteau v. District County Court, 420 U. S. 425, 447 (1975). Congressional intent therefore must be “clear” before this Court will find that a reservation established by Congress (or the Executive) was disestablished. Mattz v. Arnett, 412 U. S. 481, 505 (1973). Applying these principles, the Court has found disestablishment when Congress ratified a treaty by which Indians agreed to sell all interest in part or all of a reservation, DeCoteau v. District County Court, supra, or when Congress employed express words of termination, Mattz v. Arnett, supra, at 504 n. 22 (dictum). But when, as here, Congress merely “opened” a reservation—that is, made reservation lands available to non-Indians and acted as a sales agent on behalf of the Indians—the reservation boundaries have been held to be unaffected. Mattz v. Arnett, supra; Seymour v. Superintendent, 368 U. S. 351 (1962). In DeCoteau, the Court clearly distinguished the two situations, observing:

“[A purchase-and-sale Act] is not a unilateral action by Congress but the ratification of a previously negotiated agreement, to which a tribal majority consented. [It] does not merely open lands to settlement; it also appropriates and vests in the tribe a sum certain . . . in payment for the express cession and relinquishment of 'all’ of the *618tribe’s 'claim, right, title, and interest,’ in the unallotted lands. The statute in Mattz, by contrast, benefited the tribe only indirectly, by establishing a fund dependent on uncertain future sales of its land to settlers.” 420 U. S., at 448.

Today, however, the Court obliterates this distinction, and, by holding against the Tribe when the evidence concerning congressional intent is palpably ambiguous, erodes the general principles for interpreting Indian statutes.

I

What is perhaps most striking about the Rosebud Acts, in light of the interpretation the Court places upon them, is the absence of any express provision disestablishing the Reservation. As we observed in Mattz: "Congress has used clear language of express termination when that result is desired.” 412 U. S., at 504 n. 22. We cited three examples in Mattz: 15 Stat. 221, which stated that “the Smith River reservation is hereby discontinued”; 27 Stat. 63, which stated that “a portion of the Colville Indian Reservation . . . is hereby, vacated and restored to the public domain”; and 33 Stat. 218, enacted just two days before the first of the Rosebud Acts, which stated that “the reservation lines of the said Ponca and Otoe and Missouria Indian reservations . . . are hereby abolished,” The very Act that created the Rosebud Reservation provides yet another example, for in that Act Congress expressly “restored to the public domain” part of the Great Sioux Reservation. Act of Mar. 2, 1889, § 21, 25 Stat. 896. And other examples abound.3

The Acts in question contain no similar language. The Act of April 23, 1904, 33 Stat. 254, is a peculiarly drafted statute. In substance, it is no different from the *619statutes considered in Mattz and Seymour; it opens lands on the Reservation to white settlers, guarantees to the Indians the proceeds from the sale of the lands, but does not commit the United States to purchasing the land.4 In form, however, the Act “amended and modified” and then “ratified” the 1901 Agreement between Inspector McLaughlin and the Rosebud Sioux in which the Tribe agreed to sell the lands in question to the United States for a lump sum; this Agreement had been rejected by the Congress in 1902. The “amendments” which Congress unilaterally inserted obviously were substantial, since they transformed the transaction from a DeCoteau-type purchase to a Mattz-type “opening.” But because the ratification format was used, the 1904 Act contains language from the 1901 Agreement which provided that the “Indians belonging on the Rosebud Reservation, South Dakota, for the consideration hereinafter named, do hereby cede, surrender, grant, and convey to the United States all their claim, right, title, and interest” in the unallotted lands in Gregory County.

In DeCoteau we stated that this language, when contained in an agreement approved by the Indians and ratified by Congress, is “precisely suited,” 420 U. S., at 445, to terminating a reservation. But I cannot agree with the Court, ante, at 597, that the language is equally well suited to disestablish the Reservation here. Its usage may simply mean that Congress found that working from an earlier document—in this case the 1901 Agreement—was easier than drafting a new law. Whereas in DeCoteau the key phrase expressed the Indians’ understanding of what they were surrendering and the Government’s understanding of what it was acquiring, here the Indians had not agreed to this transaction and the Government disclaimed any intent to purchase anything other than school *620lands, see n. 4, supra. Indeed, as the Court concedes, ante, at 597, as a matter of English usage the words “cede, surrender, grant, and convey,” make no sense in the context of an “agreement” to which the seller has not assented. Thus the Court ultimately rests its decision on an asserted ability to “ ‘see what [Congress is] driving at,'” even though Congress has “ ‘not said it.'” Ibid.

The 1907 and 1910 Acts are far simpler for present purposes. They contain neither words of cession nor words of termination. They simply “authorized' and directed” the Secretary of the Interior “to sell or dispose of” the specified lands “under the general provisions of the homestead and town-site laws of the United States.” Act of Mar. 2, 1907, §§ 1, 2, 34 Stat. 1230; Act of May 30, 1910, §§ 1, 2, c. 260, 36 Stat. 448. These statutes are virtually identical to the law construed in Seymour v. Superintendent, which also “authorized and directed” the Secretary “to sell or dispose of” specified lands “under the provisions of the homestead laws.” Act of Mar. 22, 1906, §§ 1, 3, c. 1126, 34 Stat. 80-81. They are quite similar to the Act at issue in Mattz which “declared” specified lands “to be subject to settlement, entry, and purchase under the laws of the United States granting homestead rights and authorizing the sale of mineral, stone, and timber lands.” Act of June 17, 1892, 27 Stat. 52. They bear no resemblance, however, to the statutes cited in Mattz as examples of “clear language of express termination.”

II

Since congressional intent must be unambiguous before we can conclude that Congress terminated part of an Indian reservation, the absence of any express provision to this effect in the Rosebud Acts strongly militates against the interpretation the Court places on those Acts. But I need not rely on congressional silence alone—eloquent as it may be—to reject the Court’s interpretation. For both the text of the *621Acts and the circumstances surrounding their enactment affirmatively point to the opposite conclusion.

A

The text of the Acts provides numerous indications that Congress did not intend to remove the opened areas from the Reservation. First, the Acts granted the Indians a variety of rights in those areas. All three Acts, for example, permitted Indians with allotments in the counties to be opened to retain their allotments,5 and the 1907 and 1910 Acts also allowed certain Indians without allotments in these counties to secure allotments there.6 All three Acts also granted the Indians a beneficial interest in all the opened lands, since the Acts simply made the United States “trustee for [the] Indians to dispose of said lands.”7 And the 1904 and 1910 *622Acts authorized the Executive, before opening the counties to settlers, to reserve some lands for Indian schools, religious missions, and service agencies.8 Of course, it is possible that Congress intended to remove the opened counties from the Reservation while leaving the Indians with a host of rights in the counties. But this interpretation of the statutes is surely strained, especially since nothing in the legislative history indicates that such an anomalous result was desired. Thus, it is far more sensible to view these grants to the Indians as evidence that Congress did not intend to terminate the Reservation immediately.

This interpretation is supported by other provisions in the Acts as well. In the 1907 and 1910 Acts, for example, Congress directed that payments received from sale of the lands to be opened were to be deposited “to the credit of the Indians belonging and having tribal rights on the Rosebud Reservation.” 9 If the Rosebud Acts also removed the opened counties from the Reservation, then the members of the Tribe living in Gregory County, opened in 1904, were not entitled to share in the proceeds of the 1907 or 1910 sales, and the members of the Tribe living in Tripp County, opened by the Act of 1907, were not entitled to the 1910 proceeds at the very least.10 Again, it is possible that Congress intended *623this result. But, absent contrary evidence, it is far more reasonable to assume that Congress meant for all members of the Tribe living on the original Reservation to profit from the sales, since prior to the Rosebud Acts they all had equal rights in the opened lands. Thus, the manner in which Congress defined the class of beneficiaries in the 1907 and 1910 Acts indicates that Congress believed that the Indians living in the opened counties still “belonged” to the Reservation after the lands were opened.

Finally, all the statutes contain an important guide to interpretation that the Court ignores. Each Act states, in almost identical terms, that “nothing in this ‘agreement shall be construed to deprive the . . . Indians of the Rosebud Reservation, South Dakota, of any benefits to which they are entitled under existing treaties or agreements, not inconsistent with the provisions of this agreement.’ ”11 These provisions constitute clear congressional commands to interpret the Rosebud Acts so as to minimize conflicts with the Treaty of 1889. Yet the Court ignores these provisions and maximizes the conflict, by construing the Acts to limit not just the Rosebud Sioux’s land use, but also their jurisdiction.12

*624B

The Court’s construction of the Rosebud Acts is also untenable when the Acts are placed in historical context. Just as we held in Mattz that the statute at issue there was to be interpreted “from the overview of the earlier General Allotment Act of 1887, 24 Stat. 388,” 412 U. S., at 496, so, too, must the Rosebud Acts be construed from this perspective. As we observed in Mattz:

“[The policy of the General Allotment Act] was to continue the reservation system and the trust status of In*625dian lands, but to allot tracts to individual Indians for agriculture and grazing. When all the lands had been allotted and the trust expired, the reservation could be abolished. Unallotted lands were made available to non-Indians with the purpose, in part, of promoting interaction between the races and of encouraging Indians to adopt white ways.” Ibid. (footnote omitted).

This policy reflected Congress’ attempt “to reconcile the Government’s responsibility for the Indians’ welfare with the desire of non-Indians to settle upon reservation lands.” DeCoteau v. District County Court, 420 U. S., at 432. Because the “familiar forces,” id., at 431, at work on Congress demanded land for settlers, Congress opened the reservations. But because these forces were not overly concerned with the niceties of reservation boundaries, the reservation status of the opened areas was preserved until the trust period expired, to insure federal protection of the Indians while they were being “civilized” through contacts with white settlers. Thus, to interpret the Rosebud Acts as terminating three-fourths of the Rosebud Reservation is to set them at war with Congress’ general policy toward Indians at the time the Acts were approved.

III

The Court ultimately rests its construction of the Acts on an analysis of their legislative history. While there may be occasional passages in the history that suggest an intent to terminate,13 I cannot agree that such an intent is established with anything approaching the requisite clarity.

*626In the first place, the legislative history of the Rosebud Acts is extraordinarily sparse. The 1904 Act, which the Court properly regards as the crucial Act, was introduced by Representative Burke of South Dakota on January 19, 1904, 38 Cong. Rec. 902-903; was reported out of the Committee on Indian Affairs, which Mr. Burke chaired, two days later, id., at 1010; and passed the House on February 1, id., at 1469, after a debate that consumes only six pages in the Congressional Record, id., at 1423-1429.14 The bill was transmitted to the Senate the same day; was reported out of the Committee chaired by Senator Gamble of South Dakota three days later; id., at 1601; and was called up, amended, and approved by the Senate without debate on April 18, id., at 4988.15 The House concurred in the Senate amendments the following day without any discussion. Id., at 5155. The 1907 Act received *627even less congressional attention. It was approved within one month after it was introduced without any debate in the Senate, 41 Cong. Rec. 3323 (1907), and with a debate in the House that occupies only one page in the Record, id., at 3104.16 Only the 1910 Act was seriously debated by Congress, and these debates focused almost exclusively on the method by which the opened lands would be distributed to white settlers. 45 Cong. Rec. 1066-1071, 5456-5473 (1910).

In light of the brevity of the debates, it is not surprising that there is a paucity of relevant materials. The Court finds just two quotations from the debates, ante, at 596, 608, and three quotations from the Committee Reports, ante, at 595, 611, 612, that directly bear on the disestablishment issue.17 What the Court cannot find, however, is particularly telling. Unlike the debates in Mattz which revealed that “the establishment of the reservation . . . was viewed as a mistake and an injustice,” 412 U. S., at 500, there were no expressions of hostility toward the existence or size of the Rosebud Reservation. Nor were there any statements indicating that Congress intended to deviate from its general policy of preserving reservations or to abandon its role as guardian of the Indians living in the opened counties. Indeed, although Congress was *628aware that the Rosebud Acts initiated a new policy toward surplus lands18—one which removed the Government from the role of buyer and the Indians from the role of seller—at no point in the debates did anyone discuss the consequences of this change on Reservation boundaries.

The poverty of the Court’s analysis is best revealed by its treatment of the history of the crucial 1904 Act. The Court begins with “the undisputed fact that the 1901 Agreement, had it been ratified by Congress, would have disestablished that portion of the Rosebud Reservation which lay in Gregory County.” Ante, at 591. Its review of the legislative history then leads it to conclude that “there is no indication that Congress intended to change anything other than the form of, and responsibility for, payment.” Ante, at 594-595. But the fact that Congress did not expressly repudiate all of the consequences of an Agreement to which it was not a party and which it had refused to ratify hardly establishes that Congress affirmatively intended those consequences to result from the very different transaction it devised in 1904.19 It is at least *629equally plausible that Congress did not explain the effect of the 1904 Act because it assumed that the Act would have precisely the same effect as earlier nonpurchase surplus land Acts such as those considered in Mattz: The lands would be opened and the reservations preserved. Nor is the fact that Congress adopted the format of the 1901 Agreement especially probative, since this may have been done simply out of convenience.

Ultimately, what the legislative history demonstrates, as co-counsel for the State has aptly concluded, is that Congress manifested an “almost complete lack of . . . concern with the boundary issue.” 20 The issue was of no great importance in the early 1900's as it was commonly assumed that all reservations would be abolished when the trust period on allotted lands expired. There was no pressure on Congress to accelerate this timetable, so long as settlers could acquire unused land. Accordingly, Congress simply did not focus on the boundary question. Its indifference is perhaps best manifested by the fact that in legislation concerning the Reservation enacted immediately subsequent to the Rosebud Acts, Congress at times referred to the opened counties as part of the Reservation, and at times referred to them as no longer part of the Reservation.21 For the Court to find in this con*630fusion and indifference a “clear” congressional intent to disestablish the Reservation is incomprehensible.

IV

The most obvious and immediate consequence of today’s decision is jurisdictional. Even though the people of South Dakota have expressly declined to assume jurisdiction over Indian country,22 from now on crimes (or torts) committed by the Indians on nontrust land in the opened counties will be within the jurisdiction of the State. This will create an “impractical pattern of checkerboard jurisdiction,” in which “law enforcement officers . . . will find it necessary to search tract books in order to determine whether criminal jurisdiction over each particular offense . . . is in the State or Federal Government.” Seymour v. Superintendent, 368 U. S., at 358. In addition, even while on their trust lands, the almost 2,000 enrolled Indians in the opened counties will be generally subject to “state law otherwise applicable to all citizens of the State,” Mescalero Apache Tribe v. Jones, 411 U. S. 145, 149 (1973), even if the same law could not be applied to Reservation Indians because it would “interfere with reservation self-government or would impair a right granted or reserved *631by federal law,” id., at 148. This is reason enough to be troubled by today’s decision.

But beyond these jurisdictional consequences, the holding today places a grave cloud over the property rights of both the Tribe and the Indians living off the newly contracted Reservation. With respect to the Tribe, 4,600 acres in the opened counties were returned to it pursuant to the Indian Reorganization Act of 1934, 48 Stat. 984, after the Secretary found, in the words of § 3 of the Act, that these were “the remaining surplus lands of [an] Indian reservation” opened before June 18, 1934. But if the opened counties were not part of the Reservation, then the Secretary’s right to return the land to the Tribe is at least open to question.23 More seriously, the Indians living on trust lands in the opened counties have assumed that § 2 of the Reorganization Act, which extended the trust period on “Indian lands,” applied to their property. But if these counties were not part of a reservation, this assumption is dubious at best, since § 8 of the Act states that the Act shall not “be construed to relate to Indian holdings of allotments . . . upon the public domain outside of the geographic boundaries of any Indian reservation now existing . . . .” Should it be determined that the trust period was not extended, the State of South Dakota could claim crushing amounts of back taxes.

Finally, today’s decision may result in a sharp reduction in the federal aid available to members of the Rosebud Tribe living off the Reservation. The Bureau of Indian Affairs has been administering the opened counties as part of the Reservation, see n. 2, supra, and in requesting appropriations for the Reservation Indians has included Indians living in the *632opened counties, Brief for United States as Amicus Curiae 37-38. In addition, we have been advised by the Association on American Indian Affairs et al., as amici curiae, that the Rosebud Tribe has received a large amount of federal aid pursuant to a variety of federal programs. Brief 31-39. The Association reports that in the past the Tribe has been able to expend these monies for programs in the opened as well as the closed counties, because the federal agencies have viewed all the counties as part of the Reservation. Ibid. But in light of today’s decision, the Tribe’s ability to use federal funds to benefit tribal members living in these counties is in serious doubt.24

Nor are these potential consequences limited to the Rosebud Reservation. The Rosebud Acts were described by their sponsors as the beginning of a new policy with respect to surplus lands. See n. 18, supra. During the decade following the enactment of the first Rosebud Act, Congress passed 21 other statutes that opened surplus reservation lands to settlers.25 If the Rosebud Acts diminished the Rosebud Res*633ervation, then the boundaries of more than a score of other reservations must be in doubt.

Because I can find no principled justification for inflicting manifold injuries on the Rosebud Sioux Indians and for jeopardizing the rights of numerous other tribes, I respectfully dissent.