Overview
The 18th Pennsylvania Infantry (Three Months’ Service) was an infantry regiment organized in Pennsylvania for service in the Union Army during the early months of the American Civil War. The regiment was mustered in at Philadelphia on April 24 and 25, 1861, and served primarily in the Middle Department, performing garrison and guard duties in Maryland. Its service was characterized by a focus on the security of key federal installations and the maintenance of order in Baltimore during a period of heightened tension.
Organization & Service
The 18th Pennsylvania Infantry (Three Months’ Service) was formed by augmenting the 1st Regiment, 1st Brigade, 1st Division of the Pennsylvania state militia with additional recruits. The regiment was officially mustered into service at Philadelphia on April 24 and 25, 1861. Colonel William D. Lewis, Jr. commanded the unit, with Lieutenant Colonel Charles Wilhelm and Major Alexander E. Newbold as principal officers.
On May 14, 1861, the regiment moved to Perryville, Maryland, and immediately embarked for Locust Point. The unit was stationed at Fort McHenry until May 22, after which it was transferred to Baltimore. There, the regiment performed guard and police duty for the remainder of its term, with the exception of a detachment sent to Pikesville to garrison the national arsenal. Due to the ongoing need for Union troops in Baltimore, Companies B, C, D, E, G, H, K, and part of Company I were remustered into United States service on July 24, 1861, for an additional ten days. The regiment was finally mustered out at Philadelphia on August 7, 1861.
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
- Garrison duty at Fort McHenry, Maryland (May 1861)
- Guard and police duty in Baltimore, Maryland (May–August 1861)
- Garrison of the national arsenal at Pikesville, Maryland (detachment)
Casualties
Specific casualty figures for the 18th Pennsylvania Infantry (Three Months’ Service) are not detailed in available primary sources. The regiment primarily performed garrison and guard duty and did not participate in major combat operations during its term of service.
Field Officers & Commanders
- Colonel William D. Lewis, Jr.
- Lieutenant Colonel Charles Wilhelm
- Major Alexander E. Newbold
Regimental Roster
The full roster of the 18th Pennsylvania Infantry (Three Months’ Service), including officers and enlisted men, is available for genealogical and historical research. For a complete list of names and additional service details, please visit the regimental 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