There is, however, another state police force operating in Massachusetts in the 1920s, although none of its units are based in Lovecraft Country. The Metropolitan Park Commission Police was established in 1893 to police the state-run Metropolitan Park System established the same year. In 1919, with the formation of the Metropolitan District Commission (by the merger of the Metropolitan Park Commission, Metropolitan Sewer Board and Metropolitan Water Board) it was renamed the Metropolitan District Police (MDP). It existed under this name until 1992, when it was merged into the Massachusetts State Police. There's a good unofficial website on the force.
The MDP is actually considerably larger than the MSP in the 1920s. While it is primarily concerned with policing the state parks, its officers are armed, have full state police powers, and are sometimes drafted in to assist with general policing in emergencies. It has used Indian motorcycles since 1905, and now has considerable numbers of them. It also has a few cars and in addition uses horses and launches. It has police boxes installed for communications throughout the areas it polices. The MDP has a detective element (detective officers being known as inspectors) and some female patrol officers were appointed in the 1920s.
The MDP is organised into divisions, each policing a specific state park area and with its own police station, which is also usually the headquarters of that park division. The divisional superintendent is also the captain of police and is assisted by a lieutenant, 2 or more sergeants and a force of patrolmen (usually 20-30).
Blue Hills Division Station: Situated at 685 Hillside Street, Milton, it is responsible for policing the Blue Hills Reservation and is also responsible for the Stony Brook Station, which polices the Stony Brook Reservation. It is now the Milton MSP station. Contemporary photos and a modern photo.
Charles River Lower Basin Division Station: Opened in 1910. The former station is now adjacent to the current Boston MSP station, situated at 250 Leverett Circle, Boston. Contemporary photos.
Charles River Upper Basin Division Station: Opened as the Charles River Speedway (Upper Basin) District Station in 1899. Renamed in 1910. Situated at 1400 Soldiers Field Road, Brighton. It is also responsible for the Beaver Brook Station in Waltham, which polices the Beaver Brook Reservation, and the Riverside Station, which opened in Norumbega Park, Auburndale in 1904. The Brighton MSP station is now adjacent to the former divisional station. Contemporary photos.
Middlesex Fells Division Station: Located in the Roosevelt Circle area of Medford and covers the Middlesex Fells, Alewife Brook and Mystic River Reservations. It was relocated in the 1950s and is now Medford MSP station. Contemporary photo.
Nantasket Beach Division Station: Opened in 1904 at Hull. Contemporary photos.
Revere Beach Division Station: The first MDP station, opened in 1899. Situated on Revere Beach Boulevard, just across from Revere Beach (designated a public beach in 1895 and the USA's oldest), it has a distinctive tower. The lieutenant actually answers to the superintendent of the Charles River Lower Basin Division, although Revere Beach has more policemen. It is also responsible for the Nahant Beach Station, situated in the beach bathhouse. It is now Revere MSP station. Contemporary photos and a modern photo.
MDP uniforms are a distinctive light grey, with thigh-length (or longer), closed-collared jackets and the strangely small peaked caps beloved of many American police forces in that era (and still beloved of American fire departments) - they only changed from helmets at the end of the 1910s.
Contemporary photos of police launches and a police ambulance.