William A. Harn commanded a New York artillery battery in the American Civil War.
Shortly after the regiment was mustered into federal service on June 17, the company was detached and organized as a battery of light artillery.
Lt. William Stuart was in command in the Maryland Campaign, in which the battery served with the division of Brig.
When the VI Corps returned to the Petersburg front, Harn's battery rejoined its artillery brigade.
Harn received a brevet major appointment for his actions at the Battle of Spotsylvania Court House and the Richmond-Petersburg Campaign.
William Harn died of Tuberculosis on May 31, 1889, at the age of 55 and was buried in Evergreen Cemetery, Saint Augustine.
The monument to Harn's battery in the Gettysburg National Military Park, on the Taneytown Road, was made by the Smith Granite Company.