Like other Plains tribes, the Blackfeet originally lived farther east, in the forests north of the Great Lakes. As they drifted westward across the Canadian prairies, the various Blackfeet tribes evolved into a loose confederation of entities sharing a common language (an Algonquian dialect) and mutual defense of their hunting lands. These groups, later known as the Piegan, the Blood, and the Northern Blackfeet, combined to form the Blackfeet Nation, one of the largest and most feared Indian tribes.

The Piegan ventured farthest south, taking control of much of northern Montana by 1800. The Blackfeet were celebrated horsemen and warriors, and their social order was structured by membership in military societies. Men who were not militarily inclined were treated as women; first reported by French trappers, this cultural practice, called the berdache, was later found to be common in other aboriginal societies. Religious practice centered on the ritual Sun Dance and shamanistic powers derived from dreams and visions.