Gen. Robert E. Lee concentrated his full strength against Maj. Gen. George G. Meade’s Army of the Potomac at the crossroads county seat of Gettysburg. On July 1, Confederate forces converged on the town from west and north, driving Union defenders back through the streets to Cemetery Hill.

Maj. Gen. J.E.B. Stuart’s cavalry, which was riding north to get around the Union army, attacked a Union cavalry regiment, driving it through the streets of Hanover. Brig. Gen. Farnsworth’s brigade arrived and counterattacked, routing the Confederate vanguard and nearly capturing Stuart himself. Stuart counterattacked.

Companies "A," "B," "C," "D," "E," "F" and "G" organized at Camp Curtin, Pa., and mustered into State service July and August, 1861. Moved to Camp Jones, near Washington, D.C., August. Companies "H," "I" and "K" organized at Camp Wilkins, Pittsburgh, August, 1861. Joined Regiment at Washington. Company "L" organized as an Independent Company July 30, 1861. On duty at Baltimore until January, 1862; then Joined Regiment. Company "M" organized as an Independent Company August 5, 1861. At Baltimore, Md., until October 3, 1861; then on eastern shore of Maryland under Lockwood picketing and scouting until January, 1862; then Joined Regiment. Regiment attached to McCall's Division, Army of the Potomac, to March, 1862. Cavalry, McDowell's 1st Army Corps, Army of the Potomac, to April, 1862. Bayard's Cavalry Brigade, Dept. of the Rappahannock, to June, 1862. Bayard's Cavalry Brigade, 3rd Army Corps, Army of Virginia, to September, 1862. Bayard's Brigade, Cavalry Division, Army of the Potomac, to January, 1863. 2nd Brigade, 3rd Division, Cavalry Corps, Army of the Potomac, to June, 1863. 1st Brigade, 2nd Division, Cavalry Corps, Army of the Potomac, to June, 1865.