United States. Army. Corps of Engineers. .  "Map of the battlefield of Bull Run, Virginia. Brig. Gen. Irvin McDowell commanding the U.S. forces, Gen. [P.] G.T. Beauregard commanding the Confederate forces, July 21st 1861."  Map.  1877.  Norman B. Leventhal Map & Education Center,  https://collections.leventhalmap.org/search/commonwealth:ww72bp01t (accessed January 19, 2021).