The regiment was attached to Banks' Division, Army of the Potomac, to March 1862.

2nd Brigade, 1st Division, XII Corps, Army of the Potomac, July 1863.

The 1st Maryland Infantry, Potomac Home Brigade mustered out of the service August through December 1864.

Sent to Annapolis, Md., and when exchanged assigned to duty on the Potomac in southern Maryland to June 1863.

Moved from Monocacy to Harpers Ferry, West Virginia, and duty in that district until April 1865.

Under command of Col. Maulsby, the regiment formed part of 2nd Brigade (Brig.

Gen. Alpheus S. Williams), XII Corps (Maj. Gen. Henry W. Slocum) at the Battle of Gettysburg.

[1] On the morning of July 2, the regiment constructed breastworks south of Culp's Hill at McAlister's Woods.

The entire division was withdrawn later in the day and sent south to support a section of the Union line under attack by Longstreet's Corps.

Returning to Culp's Hill that evening, the regiment discovered that its breastworks had been captured by Confederates of Maj. Gen. Edward "Allegheny" Johnson's division.

On July 3, the regiment fought to hold ground against renewed attacks by Johnson's division.

Gen. Alpheus Williams wrote: "The wonder is that the rebels persisted so long in an attempt that the first half hour must have told them was useless.