Desert bighorn sheep establish two desert areas in southwestern Arizona to help preserve the desert bighorn sheep: Cabeza Prieta National Wildlife Refuge and the Kofa National Wildlife Refuge. In 1941, the San Andres National Wildlife Refuge in New Mexico was added. Desert bighorn sheep populations have trended upward since the 1960s when their population was estimated at 6,700-8,100. The upward trend was caused by conservation measures, including habitat preservation. In 1980, desert bighorn sheep populations were estimated at 8,415-9,040. A state-by-state survey was conducted a few years later and estimated the overall US desert bighorn sheep population at 15,980. The 1993 estimate of
Sevier Desert and Cedar Valleys. The east of the Sevier Desert contains the communities lying at the foothills of the mountain ranges. The Black Rock Desert volcanic field is located west of the cities. Pavant Valley lies at the west of the Pavant Range, and west of the Canyon Mountains lies the Oak Creek Sinks adjacent east of the Sevier River, and west of Oak City. The northeast perimeter of the desert lies at the southwest foothills of the East Tintic Mountains, noted for its mining. Tintic Valley, a small valley between the West Tintic Mountains feeds southwesterly into the Sevier Desert.