The Monson Railroad was a 2 ft narrow gauge railway, which operated between Monson Junction on the Bangor and Aroostook Railroad and Monson, Maine. The primary purpose of this railroad was to serve several slate mines and finishing houses in Monson. According to the Scientific American of 17 May 1890, it was the smallest railroad in the United States.

Monson is a town in Piscataquis County, Maine, United States. The population was 609 at the 2020 census. The town is located on Route 15 which is a significant route north into the well known Moosehead Lake Region, to which Monson can be considered a gateway. This route eventually leads to the Canadian Province of Quebec.