3rd Massachusetts Heavy Artillery

[Robert Gray]

Non-commissioned officers of the 3rd Massachusetts Heavy Artillery in Fort Totten.
The 3rd Regiment of Massachusetts Volunteer Heavy Artillery was a unit that served in the Union Army during the American Civil War. It was organized from already mustered unattached companies of heavy artillery raised for the defenses of the Massachusetts coast.
Beginning in January 1863, and continuing until early 1864, twelve companies of heavy artillery were raised in Massachusetts and mustered into service to garrison the military forts along the coast of the state. The units were designated "unattached" as they did not belong to a particular regiment.
In the spring of 1864, the 3rd Unattached Company, along with the 6th through 12th, were ordered to Washington, DC, where they were to garrison the forts protecting the capital. Massachusetts' Governor Andrew called for the companies to be given regimental status, and when it was granted, several other companies since raised were sent to Washington to complete its complement, and was officially made a regiment in the fall of 1864. Except for Company I, the regiment continued with its duty of manning forts in the vicinity of the capital. A portion of the regiment was mustered out on 17 June 1865, while the remaining companies served until 18 September.
[Wikipedia]