Overview
The 45th Pennsylvania Infantry (Three Years’ Service) was an infantry regiment organized at Camp Curtin, Harrisburg, Pennsylvania, and mustered into United States service on October 21, 1861. Composed of men from Centre, Lancaster, Mifflin, Tioga, and Wayne counties, the regiment served in the Union Army, primarily in the Eastern and Western Theaters. The 45th Pennsylvania Infantry is noted for its participation in major campaigns, including the siege of Vicksburg, the Knoxville Campaign, the Overland Campaign, and the siege of Petersburg.
Organization & Service
The 45th Pennsylvania Infantry was organized and mustered in for a three-year term on October 21, 1861, at Camp Curtin, Harrisburg. The regiment moved to Washington, D.C., on October 23, 1861, and was assigned to Howard’s Brigade, Casey’s Division, encamping on the Bladensburg Road. On November 19, it embarked for Fortress Monroe and remained at Camp Hamilton until December 6, before sailing to Port Royal, South Carolina. There, the regiment occupied Bay Point, Otter, and Fenwick Islands, with detachments stationed on North Edisto and John’s Islands in the spring and summer of 1862.
In June 1862, the regiment moved to James Island near Charleston, South Carolina, where it participated in engagements before returning to Hilton Head. The regiment was reunited and sent to Fortress Monroe in July, then encamped near Newport News. In August, as part of the 1st Brigade, 1st Division, 9th Corps, it moved to Brooks’ Station and Acquia Creek, Virginia, destroying railroad property and supplies. The regiment joined the Army of the Potomac in September 1862, fighting at South Mountain and being held in reserve at Fredericksburg. It wintered at Falmouth, Virginia, and later moved to Newport News and then to Kentucky in May 1863.
Arriving in Kentucky in June 1863, the regiment was quickly ordered to Vicksburg, Mississippi, where it was posted at Haines’ Bluff and participated in the pursuit to Jackson. After returning to Vicksburg, the regiment moved to East Tennessee, engaging at Blue Springs and participating in the siege of Knoxville and subsequent operations. In January 1864, 426 members reenlisted as veterans and were granted furloughs, returning to the field in May.
During the Overland Campaign, the 45th Pennsylvania fought at the Wilderness, Spotsylvania, North Anna River, and Cold Harbor. It took part in the siege of Petersburg, including the assault of June 18, 1864, and was engaged at the Weldon Railroad, the Battle of the Crater, and Poplar Spring Church, where many were captured after a desperate fight. The regiment, reinforced with recruits, fought at Hatcher’s Run in October 1864 and participated in the final assault on Petersburg on April 2, 1865. The 45th joined in the pursuit of Confederate forces, took part in the Grand Review in Washington, D.C., and was mustered out at Alexandria, Virginia, on July 17, 1865.
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
- Occupation of Bay Point, Otter, and Fenwick Islands (1861–1862)
- Operations on North Edisto and John’s Islands (May–June 1862)
- James Island (June 1862)
- South Mountain (September 1862)
- Fredericksburg (reserve, December 1862)
- Vicksburg Campaign (June–July 1863)
- Pursuit to Jackson, Mississippi (July 1863)
- Blue Springs, Tennessee (October 1863)
- Siege of Knoxville (November–December 1863)
- Wilderness Campaign (May–June 1864): Wilderness, Spotsylvania, North Anna River, Cold Harbor
- Siege of Petersburg (June 1864–April 1865): Assault of June 18, Weldon Railroad, Battle of the Crater, Poplar Spring Church, Hatcher’s Run
- Final Assault on Petersburg (April 2, 1865)
- Grand Review, Washington, D.C. (May 1865)
Casualties
According to Fox’s Regimental Losses and official reports, the 45th Pennsylvania Infantry lost a significant number of men during its service. Exact figures may vary by source, but available records indicate:
- Killed or mortally wounded: approximately 13 officers and 214 enlisted men
- Died of disease: approximately 2 officers and 177 enlisted men
- Total deaths: approximately 406
Some details are incomplete in surviving primary sources.
Field Officers & Commanders
- Colonel Thomas Welsh
- Colonel John L. Curtin
- Lieutenant Colonel James A. Beaver
- Lieutenant Colonel John I. Curtin
- Lieutenant Colonel Francis M. Hills
- Lieutenant Colonel Theodore Gregg
- Major J. M. Kilbourne
- Major John I. Curtin
- Major Edward A. Kelsey
- Major Theodore Gregg
- Major John F. Trout
Regimental Roster
The full roster of the 45th Pennsylvania Infantry (Three Years’ Service), including officers and enlisted men, is available for genealogical and historical research. The roster provides names, ranks, and service details as recorded in official state and federal records.
To view the complete roster, visit the 45th Pennsylvania Infantry (Three Years’ Service) Roster page.
Sources & References
- Official Records of the Union and Confederate Armies, Series I, various volumes
- Pennsylvania Adjutant General’s Report
- Dyer, Frederick H. Compendium of the War of the Rebellion
- Fox, William F. Regimental Losses in the American Civil War
- The Union Army, Federal Publishing Company, 1908, Volume 1