Sioux City Army Air Base closed in December 1945, but in September 1946, the airfield was opened by the Air Force Reserve. Sioux City Air Base was one of the first Air Force Reserve bases established after the war, and in December 1946, the 185th Iowa Air National Guard unit was established at Sioux City. Assigned to the new Air Defense Command (ADC) upon reactivation, the 140th Army Air Force Base Unit was activated as its host organization. The mission of the 140th AAFBU was to offer flight and ground training to all commissioned and enlisted members of the Air Force Reserve residing in Iowa, Minnesota, Nebraska, South Dakota and Wyoming.