San Tan Valley is an unincorporated area in the southeastern periphery of the Greater Phoenix Metropolitan Area, bordered by Queen Creek to the north, Florence to the south, the San Tan Mountains to the west and Gila River Indian Reservation to the southwest. The population as of 2014 is estimated to be approximately 90,000, with most residents living in planned communities. Most of the valley is part of Pinal County, with the county seat located in Florence. There is an active Chamber of Commerce and many established businesses of all sizes. It is one of the fastest growing areas in the United States.