The Department of Kansas was created from the Western Department on November 9th 1861. The Department covered the area of the Colorado Territory, Dakota Territory, Indian Territory west of Arkansas, Nebraska Territory and of course Kansas. It’s first commander was Union Brigadier General David Hunter. The Department became a part of the Union Department of Mississippi on March 11th 1862.
There would be a Union Department of Kansas two more times before the end of the war. The second time it was formed on May 2nd 1862 and included the same area except for Fort Garland in Colorado. Dakota and Nebraska Territories were taken out on October 11 1862, and the Department was once again absorbed, this time into the Union Department of Missouri. Then it came back again on January 1st 1864 with the original make up minus Fort Garland, but with Fort Smith, Arkansas added. Shortly after November 9th 1864 the Department was once again merged into the Department of Missouri.