Overview
The 123rd Pennsylvania Infantry (Nine Months’ Service) was an infantry regiment organized in Pennsylvania during the American Civil War. Recruited primarily from Allegheny County, the regiment entered United States service in August 1862 and served in the Army of the Potomac. Its term of service was for nine months, and it participated in the Eastern Theater of the war.
The regiment was attached to the 2nd Brigade, 3rd Division, 5th Corps. It saw action at Fredericksburg and was present during the Chancellorsville Campaign. The 123rd Pennsylvania Infantry was mustered out in May 1863.
Organization & Service
The 123rd Pennsylvania Infantry (Nine Months’ Service) was organized in August 1862, with most of its companies recruited from Allegheny County. The regiment mustered into Federal service at Harrisburg and departed for Washington, D.C., on August 21, 1862. Upon arrival, it was ordered to Camp Stanton and assigned to the 2nd Brigade, 3rd Division, 5th Corps, Army of the Potomac.
During the Second Battle of Bull Run in late August 1862, the regiment was stationed at Bailey’s Cross Roads to intercept stragglers and did not participate directly in the fighting. In September, the regiment was sent to Antietam but arrived after the main battle had concluded and did not engage in combat there. The unit then moved with the army to Warrenton and later encamped at Potomac Creek near Fredericksburg, remaining there until December 12, 1862.
On December 13, 1862, the 123rd Pennsylvania Infantry took part in the assault on the heights at Fredericksburg, suffering significant casualties. After the battle, the regiment returned to its previous camp and remained there until January 1863, when it moved to Falmouth. On April 28, 1863, the regiment marched with the army for the Chancellorsville Campaign. On May 1, it was posted on the left of the Union line, which was not engaged that day. On May 3, the regiment supported artillery positions and sustained a few losses. The regiment was mustered out of service at Harrisburg on May 13, 1863.
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
- Second Bull Run (stationed at Bailey’s Cross Roads; not engaged)
- Antietam (arrived after the battle; not engaged)
- Fredericksburg (December 13, 1862)
- Chancellorsville Campaign (May 1–3, 1863; in support and reserve roles)
Casualties
At Fredericksburg, the 123rd Pennsylvania Infantry suffered 152 killed and wounded. Total losses for the regiment during its nine months’ service are not fully detailed in available primary sources.
Field Officers & Commanders
- Colonel John B. Clark
- Lieutenant Colonel Frederick Gast
- Lieutenant Colonel Richard C. Dale
- Major Hugh Danver
- Major Charles D. Wiley
Regimental Roster
The complete roster of the 123rd Pennsylvania Infantry (Nine Months’ Service), including officers and enlisted men, is available for genealogical and historical research. The roster provides details on company assignments, ranks, and service records.
To view the full roster, visit the 123rd Pennsylvania Infantry (Nine Months’ Service) Roster page.
Sources & References
- Official Records of the Union and Confederate Armies, Series I, Vol. XIX, Vol. XXI
- Pennsylvania Adjutant General’s Report
- Dyer, Frederick H. “A Compendium of the War of the Rebellion”
- Fox, William F. “Regimental Losses in the American Civil War”
- The Union Army, Vol. 1 (Federal Publishing Company, 1908)