Overview
The 21st Pennsylvania Infantry (Three Months’ Service) was a volunteer regiment organized in Philadelphia, Pennsylvania, for service in the Union Army during the early months of the Civil War. Mustered in on April 29, 1861, the regiment was composed primarily of men from Philadelphia and was formed from a rifle battalion previously attached to the 1st brigade, 1st division of the state militia. The unit served in the Eastern Theater as part of General Robert Patterson’s army during its brief term of service.
This unit is distinct from any later formations of the 21st Pennsylvania Infantry with different service terms.
Organization & Service
The 21st Pennsylvania Infantry (Three Months’ Service) was mustered into United States service at Philadelphia on April 29, 1861, under the command of Colonel John F. Ballier, Lieutenant Colonel Charles Ernenwein, and Major Adolph Mehler. Shortly after organization, the regiment was ordered to Suffolk Park on May 20, 1861, and then to Chambersburg on May 28. At Chambersburg, it became part of the 1st Brigade, 1st Division of General Patterson’s army.
On June 17, 1861, the regiment crossed the Potomac River with Patterson’s forces but soon returned to the Maryland side, where it encamped. The army advanced to Martinsburg on July 2, and the 21st Pennsylvania remained there for about two weeks. During its stay in Martinsburg, the regiment was presented with a flag by the local Union-supporting German community. The regiment subsequently moved with the army to Bunker Hill, Charlestown, and Harper’s Ferry. The 21st Pennsylvania Infantry was mustered out of service at Philadelphia on August 8, 1861, upon the expiration of its three months’ term.
Research This Regiment Further
If you’d like to explore this unit’s history in more depth, regimental histories and Civil War reference works offer valuable detail.
Engagements & Campaigns
- Advance to Chambersburg, Pennsylvania (May 1861)
- Operations in the Shenandoah Valley under General Patterson (June–July 1861)
- Crossing of the Potomac River (June 17, 1861)
- Occupation of Martinsburg (July 2, 1861)
- Movements to Bunker Hill, Charlestown, and Harper’s Ferry (July 1861)
Casualties
Specific casualty figures for the 21st Pennsylvania Infantry (Three Months’ Service) are not detailed in available primary sources. The regiment did not participate in major combat actions during its term of service.
Field Officers & Commanders
- Colonel John F. Ballier
- Lieutenant Colonel Charles Ernenwein
- Major Adolph Mehler
Regimental Roster
The full roster of the 21st Pennsylvania Infantry (Three Months’ Service), including officers and enlisted men, is available for genealogical and historical research. This roster provides names, ranks, and other service details for members of the regiment.
To view the complete roster, visit the 21st Pennsylvania Infantry (Three Months’ Service) Roster page.
Sources & References
- Official Records of the Union and Confederate Armies, Series I, Vol. 2
- Pennsylvania State Adjutant General’s Report
- Dyer, Frederick H., A Compendium of the War of the Rebellion
- The Union Army, Federal Publishing Company, 1908, Vol. 1