The Spirit Lake Tribe reservation was established by Treaty between the United States Government and the Sisseton Wahpeton Sioux Bands in 1867. The Reservation is located in East Central North Dakota. The Reservation is comprised of Sisseton, Wahpeton and the Cut-Head bands of Yanktonais, who had already been placed on the Reservation. According to the Treaty of 1867 the boundaries of the Spirit Lake reservation are:
"Beginning at the most easterly point of Devil's Lake; thence along the waters of said lake to the most westerly point of the same; thence on a direct line to the nearest point on the Cheyenne River; thence down said river to a point opposite the lower end of Aspen Island, and thence on a direct line to the place of beginning."
In 2014 total enrollment of the Spirit Lake Tribe members is 7,256.
The topography of the Reservation is generally consistent with the Northern Plains region, with both flat terrain and rolling hills, and some wooded areas. The major surface water feature of the Reservation is Devils Lake, which comprises 90,000 acres of area stretched over 200 miles. There are also numerous small lakes on the Reservation, including; Twin Lakes, Spring Lake, Free Peoples Lake, Elbow Lake, and Skin and Bone Lake.
The Spirit Lake Reservation covers approximately 405 square miles primarily in Benson County, and in the Southern part is Eddy County, Nelson on the east boundary and Ramsey County to the north. Total acres as of 1998 were as follows; total tribally owned is 26,283 acres, allotted (trust) land; (trust) is 34,026 acres, U.S. Government and State is 375 acres. And fee land is 184,451 acres. Total acres within the exterior boundaries are total land 245,141 acres.
The major river surface water body is the Sheyenne River, which forms the southern boundary of the Reservation. The portion of the Sheyenne within the Reservation is approximately 50 miles long: ultimately the Sheyenne River discharges into the Red river, which flows northerly between North Dakota and Minnesota into Manitoba, Canada. Numerous small streams and springs within the Reservation also contribute flows to the Sheyenne River. In addition, the rivers and streams of the Reservation have substantial areas of associated wetlands and prairie potholes.