The 9th Pennsylvania Reserves was organized at Camp Wright near Pittsburgh, Pennsylvania on June 28, 1861 and mustered in July 27, 1861 under the command of Colonel Conrad Feger Jackson.
The regiment was attached to 3rd Brigade, McCall's Pennsylvania Reserves Division, Army of the Potomac, to March 1862.
3rd Brigade, 2nd Division, I Corps, Army of the Potomac, to April 1862.
3rd Brigade, McCall's Division, Department of the Rappahannock, to June 1862.
3rd Brigade, 3rd Division, V Corps, Army of the Potomac, to August 1862.
3rd Brigade, 3rd Division, III Corps, Army of Virginia, to September 1862.
3rd Brigade, 3rd Division, I Corps, Army of the Potomac, to February 1863.
3rd Brigade, Pennsylvania Reserves Division, XXII Corps, Department of Washington, to June 1863.
Camp at Capital Hill, Washington, until August 5, and at Tennallytown, Md., until October 10.
Moved to Camp Pierpont, near Langley, Va., October 10, 1861, and duty there until March 10, 1862.