Diamond Mountain Casino is governed by the federally recognized Susanville Indian Rancheria. Established in 1928, 30 acres were purchased for the benefit of homeless California Indians. The Rancheria consists of Paiute, Maidu, Pit River, and Washoe Indians. Since 1969, when the governing body was formed, the Rancheria has worked hard towards community development which includes a clinic, tribal office, gymnasium, pre-school, and a training center. The Rancheria now needed something new, something different, and above all, something that would benefit not only the existing Tribal members, but the ones to come in the future. In 1995, the Rancheria had an exciting plan to develop what would later become a big asset to the local area; a casino was envisioned in our future.
The Diamond Mountain Casino was completed and open for business on February 17, 1996. By 1999, the state of California would see a mass movement where California tribes were able to enter into compacts with the state's Governor in the form of Prop 5. The California Proposition 5 initiative was probably the single most substantial victory ever undertaken by a coalition of Native nations. Many predicted the campaign's defeat but because of clear goals, excellent strategy, and smart tactics, it won a resounding victory among California voters. It was a great moment in American Indian public engagement. Unfortunately, some Nevada casinos filed a lawsuit, and proposition 5 was overturned and ruled unconstitutional on a legal technicality.