In a Piegan Lodge, photograph by Edward S. Curtis, c. 1910.—Courtesy of the Edward E. Ayer Collection, The Newberry Library, Chicago
Group of Algonquian-speaking Indian peoples in Alberta, Can., and Montana, U.S., comprising the Piegan (Pikuni), the Blood (Kainah), and the Siksika, or Blackfoot-proper. Together they are referred to as Siksika, or Blackfoot, a name thought to have derived from the discoloration of their moccasins with ashes. They were among the first Algonquians to move westward from timberland to open grassland and, later, among the first to acquire horses and firearms. They were known as the strongest and most aggressive military power on the northwestern plains. At the height of their power, in the first half of the 19th century, they held a vast territory extending from northern Saskatchewan to southwestern Montana. Each group was subdivided into hunting bands led by one or more chiefs. These bands wintered separately but came together in summer to celebrate the sun dance. For three decades, beginning in 1806, the Blackfoot prevented American and Canadian settlements from forming in their territory. They signed their first treaty with the U.S. in 1855, after which they were forced into farming and cattle raising. Blackfoot descendants numbered some 90,000 in the early 21st century.