United States Regiments & Batteries > Pennsylvania > Infantry

April 20 Organized at Philadelphia and mustered in for three months service under Colonel John F. Ballier, Lieutenant Colonel Charles Ernenwein and Major Adolph Mehler
May 28 Moved to Chambersburg and attached to Geo. H. Thomas’ Brigade, 1st Division, Patterson’s Army
June 6 March to Greencastle
June 15 Cross Potomac and advance on Martinsburg Road
June 16-24 At Williamsport
June 25 At Downsville
July 2 Falling Waters
July 3 Occupation of Martinsburg
July 15 Advance on Bunker Hill
July 17 Moved to Charlestown, then to Harper’s Ferry
August Moved by rail to Baltimore to Philadelphia
August 9 Mustered out.

Colonel Ballier was authorized to recruit another regiment for three years service, which became the 98th Pennsylvania Infantry. Many men of the 21st reenlisted in the 98th.