The Sacred Buffalo Vision by Robert J. Juneau and Robert C. Juneau pg.146

The highly decentralized ownership of the lands of the Blackfeet Reservation is the obstacle against which any but the most elastic and readily adaptable plan of grazing management will shatter itself and become ineffective.

By Act of Congress of April 15, 1874, the entire northern part of Montana was set aside as an Indian reservation for the use and occupancy of five tribes of Indians, including the Blackfeet tribe. This area extended from the crest of the Rocky Mountains on the west to the west boundary of North Dakota on the east and was bounded on the north by Canada and on the south by the Missouri river, Marias River and Birch Creek.

A separate reservation for the Blackfeet Tribe was established by Act of Congress of May 1, 1888 and this tribe was restricted to a greatly reduced area in the western end of the original reservation. By an agreement with the Indians dated September 26, 1895, which was subsequently ratified by Congress, the area of the reservation was further reduced and the reservation established with its present exterior boundaries.

The Blackfeet Indian Reservation is situated at the eastern base of the Rocky Mountains immediately south of the international boundary. This reservation contains a gross area of 1,492,042.44 acres. It is bounded on the north by Canada; on the west by a meandered line forming the eastern boundary of Glacier National Park; on the southwest by a meandered line, which line is also a part of the northeast boundary of the Lewis and Clark National Forest. The southeastern boundary is formed by Birch Creek, one of the upper tributaries of the Missouri River, while the eastern boundary is formed partly by Cut Bank Creek and for 24 miles by a surveyed north and south line which includes four sections of Range 6 West, Montana Principal Meridian, within the reservation.
-The Sacred Buffalo Vision by Robert J. Juneau and Robert C. Juneau  
pg.146