The River Road Stone Arch Railroad Bridge is a historic bridge carrying the former Air Line Railroad right-of-way over River Road in Salmon River State Forest in Colchester, Connecticut. It is a round-arch masonry structure, made out of mortared ashlar brownstone. The arch has a span at its base of 22 feet (6.7 m) and is 18 feet (5.5 m) high. The sidewalls of the bridge rise 4 feet (1.2 m) above the former height of the tracks, and all four corners of the bridge wing walls extend the structure. The bridge was built in 1887, as part of a state-mandated program to replace grade crossings on railroad rights-of-way with bridges.