The 124th Pennsylvania Infantry was organized at Harrisburg, Pennsylvania, and mustered in August 1862 for nine month's service under the command of Colonel Joseph W. Hawley.

The regiment was attached to 1st Brigade, 1st Division, XII Corps, Army of the Potomac, to October 1862.

Camp near Fort Albany, defenses of Washington, until September 7.

March to Fredericksburg, Va., December 10–15; then to Fairfax Station.

Burnside's 2nd Campaign, "Mud March," January 20–24, 1863.