On July 27, 1861, Major General George B. McClellan issued General Orders, No. 1 (Division of the Potomac) announcing that he was assuming command of the Division of the Potomac.
General Orders, No. 1
Headquarters Division of the Potomac
Washington, July 27, 1861
In accordance with General Order, No.47, of July 25, 1861, from the War Department, the undersigned hereby assumes command of the Division of the Potomac, comprising the Military Departments of Washington and Northeastern Virginia, Headquarters for the present at Washington.
The following named officers are announced upon the Division staff:
Brevet Major S. Williams, Assistant Adjutant General.
Major J. G. Barnard, Corps of Engineers.
Captain S. Van Vliet, Assistant Quartermaster.
Captain H. F. Clarke, Commissary of Subsistence.
Major W. F. Barry, 5th Artillery, Chief of Artillery.
Geo. B. McClellan,
Major General U.S. Army