Muster rolls and returns were originally arranged as MM 18.

The 50th Regiment Massachusetts Volunteer Infantry was organized at Camp Stanton in Boxford, Massachusetts in 1862 and was comprised of militia companies from Middlesex and Essex Counties, including the 7th Regiment of the state militia. Company A and B were mustered into service on September 15, 1862, while the following eight companies were mustered by September 30, 1862. The regiment moved to New York and then to New Orleans, Louisiana before being assigned to garrison duty in Baton Rouge and Port Hudson, Louisiana. The regiment returned to Boston, Massachusetts in August 1863. Company A was from Salem, Massachusetts and commanded by Captain George D. Putnam. This company, also known as the Salem Light Infantry, had previously enlisted with the 8th Regiment and served three months. It was considered one of the oldest militia organizations in the state, having been chartered on May 1, 1805. The company was officially mustered out of service on August 24, 1863.

This series includes company rolls, orders, reports and returns relating to the military service of the 50th Regiment Massachusetts Volunteer Infantry, Company A.