On February 2, 1863, the U.S. War Department issued General Orders, No. 134 placing Major General Samuel P. Heintzelman in command of the newly created Department of Washington.
General Orders, No. 134
War Dep’t, Adjutant General’s Office,
Washington, February 2, 1863
The district of country north of the Potomac river from Piscataway creek to Annapolis Junction, and the mouth of the Monocacy ; and south by Goose creek and Bull Run mountain, to the mouth of the Occaquan, will constitute the Department of Washington, and troops in that Department will constitute the Twenty-second Army Corps; to be commanded by Major General Heintzelman.
By Order of the Secretary of War:
L. THOMAS, Adjutant General.