Mount Graham, or Dził Nchaa Sí'an, is the highest summit in Arizona’s Pinaleño Mountains and the southernmost land in the continental United States above 10,000 feet. Sacred to Western Apache and other Native peoples, it lies near the edge of the Chiricahua Apache homeland and is one of the Western Apache’s four holiest mountains. Its isolated high country contains perennial stream headwaters, five botanical zones, relict Ice Age plant and animal populations, ancient conifers, the threatened Mount Graham red squirrel, and both native Arizona trout species. Since 1988, telescope development at the Mount Graham International Observatory has remained controversial because of both its sacred status and sensitive habitat.