The Pennsylvania 12th Infantry Regiment (3 months) was organized at Pittsburg April 22, 1861. Moved to Harrisburg, Pa., April 24; thence to York, Pa., April 25 and duty there till May 25. Attached to 3rd Brigade, 1st Division, Patterson's Army. Guard duty on Northern Central Railroad from State line to Baltimore Md. Headquarters at Cockeyville, Md., till August. Mustered out August 5, 1861. Companies of the Pennsylvania 12th Infantry Regiment Company A - Pittsburg, Allegheny County Company B - Pittsburg, Allegheny County Company C - Pittsburg, Allegheny County Company D - Pittsburg, Allegheny County Company E - Washington, Washington County Company F - New Castle, Lawrence County Company G - Monongahela City, Washington County Company H - New Castle, Lawrence County Company I - Pittsburg, Allegheny County Company K - Pittsburg, Allegheny County