As part of the New England transportation monopoly organized by the New York, New Haven & Hartford Railroad, the SR&RL operated as a subsidiary of the Maine Central Railroad from 1912 until receivership in 1923. Maine Central built 37 box cars, 37 flat cars, 3 cabooses and a baggage-RPO car in their Portland Terminal Company shops for the SR&RL between 1912 and 1917. SR&RL locomotives 15, 16, 17 and 18 were reboilered in the Maine Central Waterville shops during the same period, and a freight branch was built from Perham Junction to Barnjum.