Grant county is located in the southwestern part of the state and calls Carson its county seat. The county population on July 1, 1999, was 2,854, a decrease of 695 over the 1990 census.

The Heart Butte Dam and Lake Tschida are situated in the northwestern section of the state and provide the county with fishing, hunting, boating and skiing as well as other activities. Rivers flowing through the county include the Heart and the Cannonball (which forms the southeast boundary with Sioux County). Cedar Creek forms the southern boundary with Sioux County before draining into the Cannonball. All of these flow in an easterly direction to eventually empty into the Missouri River/Lake Oahe.