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
Desert View Watchtower contains a gift shop while the upper floors serve as an observation deck from which visitors to the national park can view eastern portions of the Grand Canyon. In 2008, two tourists were banned from all American national parks for the period of a year after using white-out and permanent marker to correct the punctuation on a sign on the Desert View Watchtower, which had been painted by Colter. Desert View Watchtower Desert View Watchtower, also known as the Indian Watchtower at Desert View, is a -high stone building located on the South Rim of the Grand Canyon within Grand