The 91st PA was in the 3rd Brigade (Gen. Weed) of the Second Division (Gen. Ayres) of the Fifth Army Corps (Gen. Sykes), of the Army of the Potomac (Gen. Meade). They were camped near Frederick Maryland on the 28th of June. By midnight or 1 AM of the 2nd of July they had marched 55 miles in 3 days, and were near Gettysburg. The Union forces were arranged in a fishhook, with the hook in the north, and the shank going south along Cemetery Ridge. On July 2nd, the Second Division was in reserve, and was moved where the fighting was fiercest. By mid-afternoon they were in the southern part of the battlefield, where the Third Army Corps, under General Sickles, had advanced beyond their assigned position, and was under heavy attack. General Warren, the Army's Chief Engineer, noticed that Little Round Top was undefended, and realizing that its loss would allow the Confederate Army to control the Union Army, General Sykes agreed to send troops. General Warren sent Vincent's Brigade. General Sykes then ordered Weed's Third Brigade there, but General Sickles (commanding the Third Corps) intercepted them and ordered them to support his troops. General Warren managed to divert one regiment (the 140th New York), and when General Sykes learned what had happened, he immediately ordered the other three regiments of the Second Division back to the Little Round Top. Before they arrived, the 140th New York had driven back the Confederate attack. Little Round Top continued under attack from sharpshooters, but didn't again face fighting as heavy. Three enlisted men of the 91st were killed, and two officers and fourteen enlisted men were wounded. (20 officers and 205 enlisted men, excluding pioneers and musicians, were engaged in the battle.) Despite the lack of heavy fighting on the 3rd, fourteen of the seventeen casualties listed in Bates occurred on the 3rd, not the 2nd. The Confederates shelled Little Round Top before Pickett's Charge, and William S Reiff was held up returning with coffee because of the heavy firing.
The property of Jacob Bolin (who later served in company G) was damaged in the battle.
- Organization of the Army of the Potamac at the battle of Gettysburg
- Brigade report (Colonel Garrard)
- Division report (Brigadier General Ayres)
- Corps report (General Sykes)
- Pennsylvania Memorial, 91st PA plaque (Gettysburg PA)
- Bates, pp.189-190
- William Coffin Reiff. 'Coffee on Little Round Top, Gettysburg'. National Tribune 19 May 1904.
- William Coffin Reiff. 'The soldier that was not buried'. National Tribune 17 August 1905, page 3, column 6.
- [death notice, Stephen Kelly]. Gettysburg PA Compiler 5 February 1889
- William Coffin Reiff. 'Tortured for sleep'. National Tribune 25 May 1905, page3, columns 3-4
- William C Reiff. 'Struggle for the Union. Trials of a boy in the Gettysburg campaign'. National Tribune 6 August 1896.
- William C Reiff. 'Josie and I at Gettysburg'. Gettysburg Compiler 9 August 1911.
- William C Reiff. 'Prisoner by the scalp'. National Tribune 28 February 1895, page 3
- letter, Sinex to Fowler, 25 March 1864 [reports number engaged], and circular, HQ 91st PA, 26 March 1864 [which asks company commanders for the numbers engaged]
- letter listing battles, Sellers to Bennett, 24 September 1864 [lists 2 and 3 July]
- letter listing battles, Sellers to Bennett, 10 November 1864
- 'Gettysburg'. Philadelphia Inquirer, 30 August 1883. [the 1883 encampment, including dedication of a 91st PA memorial]
- 'Decorates his own grave' [re Stephen Kelly]. Rocky Mountain News (Denver CO), 30 June 1886 page 8 column C
- 'A man twice dead' [re Stephen Kelly]. Weekly Register-Call (Central City CO), 15 February 1889 (issue 35), column F
- 'Monument commission' (Philadelphia Inquirer 9 March 1888 page 3)