[Manuscript Civil War Map signed by G.K. Warren] Map of Field Occupation of Army of the Potomac.  Prepared by order of Gen. Hooker from reconnaisances made under Capt. R.S. Williamson, Lt. N. Bowen, Gen. D.P. Woodbury and others.  Sent from Top'l Eng'rs office February 25, 1863 . . .  By G.K. Warren