The 12th New Hampshire Infantry was organized in
Concord, New Hampshire, and mustered in for a three-year enlistment on September 10, 1862, under the command of
Colonel Joseph Haydn Potter. The regiment was attached to Casey's Division, Military District of Washington, to December 1862. 2nd Brigade, 3rd Division,
III Corps,
Army of the Potomac, to June 1863. 1st Brigade, 2nd Division, III Corps, Army of the Potomac, to July 1863. Marston's Command, Point Lookout, Maryland, District of St. Mary's, to April 1864. 2nd Brigade, 2nd Division,
XVIII Corps,
Department of Virginia and North Carolina, to December 1864. 2nd Brigade, 3rd Division,
XXIV Corps,
Department of Virginia, to June 1865. The 12th New Hampshire Infantry mustered out of service June 21, 1865. ==Detailed service==