The Absaroka - Beartooth Wilderness contains one of the largest single expanses of land above 10,000 feet in elevation in the United States. The U.S. Forest Service set aside portions of the region as primitive areas in 1932, and Congress designated it a wilderness area in 1978. In 1983, visitors spent 392,000 collective days there, making it the fourth most visited wilderness in America at that time. Artifacts and pictographs indicate that people have hunted in these mountains for thousands of years, but it has always been country for people to visit, not live in. Reserved by treaty for the Crow in 1851, the tribe shared with the less-rugged mountains on the west side of the wilderness their name for themselves, Absaroka, while the rugged mountains on the east side they named Beartooth after a tooth-shaped peak south of Red Lodge. Gold discoveries in the 1860s attracted prospectors to Emigrant Gulch, and an 1880 treaty moved the reservation boundary eastward to allow clandestine mining claims to be developed in the mountains. The entire wilderness is a watershed for the Yellowstone, the longest undammed river left in the United States, which flows over 670 miles from its sources out of Yellowstone National Park and is the lifeblood of about one-third of Montana and much of northern Wyoming.