The Aqueduct Bridge (also called the Alexandria Aqueduct) was a bridge between Georgetown, Washington, D.C., and Rosslyn, Virginia. It was built to transport cargo-carrying boats on the Chesapeake and Ohio Canal in Georgetown across the Potomac River to the Alexandria Canal. The same eight piers supported two different bridges: a wooden canal bridge (a wooden roadway bridge was added on top of the canal later) and an iron truss bridge carrying a roadway and an electric trolley line. The bridge was closed in 1923 after the construction of the nearby Key Bridge.