Urban development is allowed within an urban growth boundary, while areas outside the boundary are preserved as rural or agricultural land. UGBs contain development within predetermined areas and preserve the surrounding open space, agricultural lands, watersheds, and other valuable lands. UGBs are generally designated to accommodate growth for a significant period of time - typically 20 years or more and they are updated periodically. The first metropolitan area to establish an UGB was Lexington, KY in 1958, however, Portland (OR, in 1979) is the most well known. Case/Example: Portland (OR) and Lexington (KY). Source/Reference: Georgia DCA, 1998, pp. 28; Nelson and Duncan, 1995, pp. 75; NACo, JCSC, and SGN, 2001, pp. 31.