The Trans-Mississippi theater refers to military operations west of the Mississippi, encompassing most of Missouri, Arkansas, most of Louisiana, and the Indian Territory in present-day Oklahoma. The Trans-Mississippi District was formed by the Confederate States Army to better coordinate Ben McCulloch's command of troops in Arkansas and Louisiana, Sterling Price's Missouri State Guard, as well as the portion of Earl Van Dorn's command that included the Indian Territory and excluded the Army of the West. The Union's command was the Trans-Mississippi Division, or the Military Division of West Mississippi.