Foss State Park occupies 1,749 acres on Foss Lake in southwestern Custer County and centers on a reservoir created in 1961 when the United States Bureau of Reclamation built Foss Dam across the Washita River. The dam and lake were designed not only for recreation but also to regulate river flows and provide water to nearby communities through an aqueduct and lateral system. The park has become one of western Oklahoma’s main outdoor recreation areas, with boating, fishing, swimming, trails, horseback riding, picnic areas, and extensive camping facilities. Since June 15, 2020, it has also been among Oklahoma parks charging a vehicle entrance fee to support maintenance and improvements.