This regiment was recruited during the summer and fall of 1861 by Col. Hartranft for three years' service, most of the officers and men having served for the three months' term. Cos. A, C, D, F and I were recruited in Montgomery county; E, H and K in Union and Snyder; G in Center and B in Northampton. The place of rendezvous was Camp Curtin, Harrisburg, and the regimental organization was completed on Nov. I6 1861. Two days later it left for Annapolis, Md., where it remained, perfecting itself in drill and discipline, until Jan. 6, 1862, when it was assigned to the 2nd brigade (Gen. Reno), Burnside's corps, embarked as a part of Burnside's expedition to North Carolina, and landed at Roanoke island on Feb. 7, 1862.

The 51st PA shared in the capture of the enemy's works here on 8 Feb 1862 and was active at the battle of New Berne, N. C., in March 1862, where it executed a gallant charge. It was again active in the battle of Camden, losing 3 killed and 21 wounded.

The 51st PA returned to Fortress Monroe in July, 1862 and was assigned to the 2nd brigade, 2nd division, 9th corps, Gen. Ferrero commanding the brigade. It was active at the second Bull Run and Chantilly, and in Sept., 1862, moved with the 9th corps on the Maryland campaign. It skirmished with the enemy's cavalry at Frederick, Md.; was hotly engaged at South mountain and again at Antietam, where its losses were 125, including Lieut.-Col Bell, and Lieuts. Beaver and Hunsicker killed; Capts. Bolton and Hart, Adjt. Shorkly, Quartermaster Freedly and Lieut. Lynch wounded. Maj. Schall was now promoted to lieutenant-colonel, and Capt. Bolton to major.

The command suffered severely in the fierce fighting at Fredericksburg in December, 1862, its losses being I2 killed and 74 wounded. It was ordered to Fortress Monroe in March, 1863, brigaded with the 51st N. Y., 2Ist Mass., and IIth N. H., and moved thence, with two divisions of the 9th corps, to Kentucky, being posted successively at Winchester, Lancaster, Crab Orchard and Stanford.

In June, 1863 the 51st PA moved with its corps under command of Gen. Parke to the support of Grant at Vicksburg, arriving on the 14th and going into camp at Mill Dale. It was employed here and at Oak ridge for several weeks in building fortifications, and joined Sherman in his campaign to Jackson in July.

The command then returned to Kentucky, encamping at Camp Nelson, where it rested and refitted after its arduous service in Mississippi during the fall of 1863. The regiment moved from Camp Nelson to Crab Orchard, where a number of recruits were received, and thence to Knoxville, Tenn. It was active at the battle of Campbell's station, and suffered all the hardships endured by Burnside's army, when besieged in Knoxville by the enemy under Longstreet. After the siege was raised it joined in the pursuit of the enemy, skirmishing with his rear-guard at Rutledge, and later went into winter quarters at Blaine's cross-roads, where the men suffered much from the meager supplies of food and clothing received.

On Jan. 5, 1864, the regiment reenlisted for a term of three years and returned to Pennsylvania on 30 days, veteran furlough. While at home the command was rapidly recruited to the maximum strength, as it was a very popular organization, and on the expiration of its furlough it proceeded to Annapolis, where it was assigned to the Ist brigade, Ist division, 9th corps, Col. Hartranft commanding the brigade and Lieut.-Col. Schall the regiment. The 51st participated in all the sanguinary engagements leading up to the siege of Petersburg, losing heavily.

Dating from the battle at the Ny river, May 12, Col. Hartranft was promoted to brigadier-general, Lieut.-Col. Schall became colonel, Maj. Bolton lieutenant-colonel, and Capt. Hart major. In the fierce fighting at Cold Harbor Col. Schall was killed while leading a charge and was succeeded in command by Lieut.-Col. Bolton. The command arrived in front of Petersburg on the 17th and at once engaged the enemy. It was in action again the next day, capturing and holding a position close to the enemy's works. This position was so exposed that a constant fire was kept up, night and day, for more than two weeks, one-third of the men being constantly employed to hold the position. It formed part of the assaulting column at the explosion of the mine, but was ordered back before it entered the crater. In this advance, Col. Bolton was severely wounded and Maj. Hart succeeded to the command. The regiment remained on duty in front of the crater for a few days, when it was relieved, and remained encamped in the rear until Aug. 19, 1864.

The 51st PA shared in the movement for the capture of the Weldon railroad, and participated in all the subsequent operations of the brigade, including the engagements at Poplar Spring Church, Ream's station, Hatcher's run, and the final assault on Petersburg, April 2, 1865.

It was mustered out at Alexandria, Va., July 27, 1865, after four years of most trying service. The Regiment lost during service 12 Officers and 165 Enlisted men killed and mortally wounded and 137 Enlisted men by disease. Total 314.