The traditional territorial lands of the Mandan, Hidatsa, and Arikara encompassed an area of more than 12 million acres extending from east of the Missouri River to Montana and south as far as present day Nebraska and Wyoming. The Fort Laramie Treaty of 1851 and subsequent executive orders and congressional acts between 1851 and 1910 reduced the original size of the reservation from roughly 12 million acres to 500,000 acres of Indian-owned land.
The Fort Berthold Reservation is situated in western North Dakota. The reservation occupies sections of six counties: Mountrail, McLean, Dunn, McKenzie, Mercer, and Ward. The total area within the boundaries of the reservation is nearly one million acres, of which about 50 percent is trust land. Lake Sakakawea covers nearly 155,000 acres of reservation land and about 600 miles of reservation shoreline. Currently, the reservation acreage is more than 988,000 acres of which 378,604 acres are individually allotted, 353,790 acres are in the returned homestead area, and 152,300 acres are in the reservoir taking area. (North Dakota Blue Book)
|*Includes approximately 152,300 acres that resulted from the creation of Lake Sakakawea.
*Includes returned homestead land, 353,790 acres.