Napa County has maintained a rural agricultural environment in a large part of the valley floor while neighboring Sonoma, Solano, and Yolo counties have allowed large tracts of former farmland to be rezoned for commercial and residential development. In 1968 vintners and civic leaders in the county seized an opportunity to preserve farmland by taking advantage of the Williamson Act enacted by the California Legislature to give landowners property tax relief for designating their land for agricultural purposes. This agricultural preserve on the floor of the valley in unincorporated areas between Napa and Calistoga was the first of its kind in the state. Initially, the preserve encompassed ,but it has grown to more than . In 2010, legislation was passed by the California State Senate and State Assembly and sent to the Governor for signing in the form of Senate Bill 1142. This bill was created to provide relief stream of funding to augment the Williamson Act.