The Blackfeet Nation, officially named the Blackfeet Tribe of the Blackfeet Indian Reservation of Montana, is a federally recognized tribe of Siksikaitsitapi people with an Indian reservation in Montana. Tribal members primarily belong to the Piegan Blackfeet (Ampskapi Piikani) band of the larger Blackfoot Confederacy that spans Canada and the United States.
The Blackfeet settled in the region around Montana beginning in the 17th century. Previously, they resided in an area of the woodlands north and west of the Great Lakes. They were a powerful force, controlling an area that extended from current day Edmonton, Alberta Province, nearly to Yellowstone National Park, and from Glacier Park to the Black Hills of South Dakota. Adjacent to their reservation, established by Treaty of 1896, are two federally controlled areas: the Lewis and Clark National Forest, set up in 1896, which contains the Badger-Two Medicine area, a significant sacred site for the tribe.
Resource: https://en.wikipedia.org/wiki/Blackfeet_Nation