Six companies were ordered to City Point, Virginia, September 1864 and attached to Benham's Engineer Brigade to December 1864.
Clough's Provisional Brigade, Ferrero's Division, Defenses of Bermuda Hundred, Virginia, to March 1865.
Moved to South Side Railroad and duty at Ford's Station until April 20.
Company K served its entire term of service at Galloupe's Island in Boston Harbor and mustered out May 6, 1865.
The six original companies of the 18th New Hampshire Infantry mustered out of service June 10, 1865.