Assiniboin (əsĭnˈəboinˌ) [key], Native North Americans whose culture is that of the N Great Plains; their language belongs to the Siouan branch of the Hokan-Siouan linguistic stock (see Native American languages). At the time of the first contact with European settlers they had no permanent village sites; they moved about as their search for food required. They were a branch of the Yanktonai Dakota, who moved north and westward prior to the 17th cent. to the region of Lake Winnipeg; later they went to the upper Saskatchewan and the upper Missouri rivers. After the acquisition of horses and firearms in the 18th cent. they became a typical Plains tribe. They were allied with the Cree against the Blackfoot. A large tribe at the time of contact, they were decimated by smallpox in the early 19th cent. There were 5,500 Assiniboin in the United States in 1990, most living on the Fort Belknap and Fort Peck reservations in Montana. Around 1,500 Assiniboin live on reserves in Saskatchewan and Alberta, Canada.
See M. S. Kennedy, ed., The Assiniboines (new ed. 1961); D. Kennedy, Recollections of an Assiniboine Chief, ed. by J. R. Stevens (1972); E. T. Denig, Five Indian Tribes of the Upper Missouri (1975).