The only issue here is whether unrecorded maps and surveys which fail to show a subdivision of land support an offer of dedication in favor of the State of North Carolina. Defendants argue that an unrecorded survey or map, which does not reflect a subdivision of land, may not form the basis of a dedication to a state or agency. They argue that the plat or map must be recorded before a dedication becomes effective and that the landowner must have intended to make a dedication. In addition, they argue that the plats here do not reflect a subdivision of lots for sale. They rely on G.S. 136-96 and G.S. 136-102.6 to support their argument that the plat or survey must be recorded. After careful review, we disagree.

“Generally, where lots are sold and conveyed by reference to a plat which represents the division of a tract into streets and lots, recordation of the plat is an offer to dedicate those streets to the public.” Tower Development Partners v. Zell, 120 N.C. App. 136, 141, 461 S.E.2d 17, 20 (1995). However, under a common law dedication, subjective intent to make a dedication and a recording of the plat is unnecessary. Tise v. Whitaker, 146 N.C. 374, 376, 59 S.E. 1012, 1013 (1907). An implied dedication can arise out of the acts of the owner. Id. at 376. “A map or plat referred to in a deed becomes part of the deed and need not be registered.” Kaperonis v. Highway Commission, 260 N.C. 587, 597, 133 S.E.2d 464, 471 (1963) (quoting Collins v. Land Co., 128 N.C. 563, 565, 39 S.E. 21, 22 (1901)). Therefore, as long as the landowner has notice of the plat through his deed, the plat does not have to be recorded in order to effect a right of way dedication. Once a right of way dedication has taken place and becomes open to the public and at least part of the area is maintained, the period of use becomes immaterial and the dedication becomes irrevocable. Steadman v. Pinetops, 251 N.C. 509, 516, 112 S.E.2d 102, 107 (1950).

*502 Here the defendants’ deeds referred to plats that showed the 100 foot right of way. In addition, the defendants allowed public utilities, without easements, to place utility poles on the defendants’ land more than 30 feet from the center of Wendover Avenue. The DOT correctly argues that this shows objectively an intent to dedicate a 50 foot right of way. In 1940, the State Highway Commission also set concrete right of way monuments on the Haggerty, McIntosh and Willard properties which should have put the defendants on notice of the 50 foot right of way being claimed by the Highway Commission. Finally, the tax cards for Stevens,’ McIntosh’s and Haggerty’s predecessors showed that the defendants were not paying ad valorem taxes on the land within the 100 foot right of way. This further suggests that the defendants had notice of and intended or acquiesced in the right of way being claimed by the DOT.

Affirmed.