The 5th New Hampshire Infantry was organized in Concord, New Hampshire and mustered in for a three-year enlistment on October 22, 1861, under the command of Colonel Edward Ephraim Cross.

The regiment was attached to Howard's Brigade, Sumner's Division, Army of the Potomac, to March 1862.

1st Brigade, 1st Division, II Corps, Army of the Potomac, to July 1863.

1st Brigade, 1st Division, II Corps, Army of the Potomac, to June 1865.

The 5th New Hampshire Infantry mustered out of service June 28, 1865, and was discharged July 8, 1865.

Peach Orchard, Allen's Farm and Savage's Station June 29.

White Oak Swamp and Glendale June 30.

Movement to Fortress Monroe, then to Alexandria and to Centreville, Va., August 16–30.

Advance up Loudoun Valley and movement to Falmouth, Va., October 29-November 17.

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

Moved to Point Lookout, Md., November 8–13, and duty there guarding prisoners until May 27, 1864.

Moved to Cold Harbor, Va., May 27-June 1, and joined the Army of the Potomac.

Deep Bottom, north of James River, July 27–28.

Mine Explosion, Petersburg, July 30 (reserve).

Dabney's Mills, Hatcher's Run, February 5–7, 1865.