4th Massachusetts Heavy Artillery Regiment

August, 1864

Organized for one year's service by consolidation of the 17th, 18th, 19th, 20th, 21st, 22nd, 23rd, 24th, 25th, 26th, 27th and 28th Unattached Companies Heavy Artillery.

November 12

Consolidated to a Regiment; Attached to 3rd Brigade, DeRussy's Division, 22nd Army Corps, Dept. of Washington and garrison duty in the Defenses of Washington, south of the Potomac

June 17, 1865

Mustered out