Dunn county is located in the West Region with Manning serving as the county seat. The county population on July 1, 1999, was 3,457, a decrease of 548 over the 1990 census.
The northeastern section of the county contains part of the Ft. Berthold Indian Reservation and abuts Lake Sakakawea. The Killdeer Mountains to the northwest are on the edge of the North Dakota Badlands/Little Missouri National Grassland area and supports viable populations of Ruffed Grouse, Mallard and Wild Turkey for the sportsmen. The mountains are 10 miles long and rise 600 feet above the surrounding countryside. Just east of this range Little Missouri State Park provides primitive shelter for hikers and horseback riders.
The central section of the county offers Lake Ilo and Lake Ilo National Wildlife Refuge to hunters and fishermen while the southern portion of the county is dominated by grasslands and the Knife River which flows west to east.