The regiment initially consisted of eleven companies of infantry, two light batteries, and two troops of cavalry, the whole being known as the "10th Legion".

The regiment was attached to 1st Brigade, Casey's Division, Army of the Potomac, to March 1862.

1st Brigade, 3rd Division, IV Corps, Army of the Potomac, to June 1862.

2nd Brigade, 3rd Division, XVIII Corps, Department of North Carolina, January 1863.

2nd Brigade, 2nd Division, XVIII Corps, Department of the South, to April 1863.

2nd Brigade, 1st Division, Morris Island, South Carolina, X Corps, July 1863.

Davis' Brigade, Folly Island, South Carolina, X Corps, to August 1863.

Saxton's Division, District of Beaufort, South Carolina, X Corps, to April 1864.

The 56th New York Infantry mustered out October 17, 1865 at Charleston, South Carolina.

Moved to Fort Monroe, Va., August 16–22, then to Yorktown, Va. Duty there and at Gloucester Point until December 26.

Moved to Morehead City, N.C., December 26-January 1, 1863; then to Port Royal, S.C., January 28–31.

Duty in Northern and Western Districts of South Carolina until September.