Any member of various North American Indian peoples that inhabited the high plateau between the Rocky Mountains on the east and the Cascade Range on the west.
The Plateau culture was not stable. By AD 1200–1300 the "classic" phase had emerged, characterized by permanent winter villages with semi-subterranean earth lodges along the main rivers and by summer camps with mat-covered conical lodges in the meadows. During the centuries that followed, the Plateau area was influenced by cultural elements from the highly specialized Northwest Coast culture. Part of this diffusion was possibly brought about by a Chinook group, the Wishram, who migrated from the coast into the Cascade Mountains. During the 18th century there were influences from the east. The Shoshone had acquired horses by that time and furnished their closest neighbours on the Plains and the Plateau with horses. Other elements of Plains culture, such as beaded dresses, warbonnets, and tepees, came with the horse. Among this group were the Coeur d'Alene, Flathead , Klamath , Kutenai, Modoc , Nez Percé , Spokan, Thompson, and Salish.