The Department of the Platte was a military administrative district established by the U.S. Army on March 5, 1866, with boundaries encompassing Iowa, Nebraska, Dakota Territory, Utah Territory and a small portion of Idaho. With headquarters in Omaha, the district commander oversaw the army's role initially along the Overland route (or Oregon Trail) to Salt Lake City, then later the construction route of the Union Pacific Railroad. The district also included the Montana road (or Bozeman Trail) through eastern Wyoming.