The Northern Arapaho Tribe of Wyoming is one of four groups of Arapaho who originally occupied the headwaters of the Arkansas and Platte Rivers. They speak a variation of the Algonquin language, and are that people's most southwest extension. Culturally, they are Plains Indians, but socially and historically distinct. After signing the Treaty of 1851, the Arapaho and Cheyenne then shared land encompassing one-sixth of Wyoming, one-quarter of Colorado and parts of western Kansas and Nebraska. Later, when the Treaty of 1868 left the Northern Arapaho without a land base, they were placed with the Shoshone in west central Wyoming, on the Wind River Reservation. The Northern Arapaho are a federally recognized tribe.