On April 4, 1862, the U.S. War Department issued General Orders, No. 34, creating the Department of the Shenandoah, under the command of Nathaniel P. Banks, and also defining George B. McClellan's command.
General Orders, No. 34.
War Dep’t, Adjutant General’s Office,
Washington, April 4, 1862.
I. – That portion of Virginia and Maryland lying between the Mountain Department and the Blue Ridge, shall constitute a Military Department to be called the Department of the Shenandoah, and under the command of Major general Banks.
II. – That portion of Virginia east of the Blue Ridge and west of the Potomac and the Fredericksburg and Richmond Railroad, including the District of Columbia and the country between the Potomac and Patuxent, shall be under the command of Major General McDowell.
By Order of the Secretary of War: