The Department of the Northwest was an Army Department created September 6, 1862 by the Union Army to put down the Sioux uprising in Minnesota. It was composed of the forces within the territory of the states of Wisconsin (taken from the Dept. of the Ohio), Minnesota and Iowa (from the Department of the Mississippi), and the Nebraska and Dakota Territories (from the Department of Kansas).Nebraska Territory was detached to the Department of the Missouri on Oct. 11 1862.