The Georgetown Car Barn, officially named the Capitol Traction Company Union Station, is at 3600 M St., on the corner of Prospect St. (and next to the Exorcist stairs) and across the street from Key Bridge. It was built in 1895 by D.C. architect Waddy B. Wood, who designed a complex building with multiple levels for different street car lines, passenger stations, and offices. It was originally designed to carry four lines, including the M St. line and a line from Rosslyn across the Aqueduct Bridge, whose remaining foundations can be seen next to Key Bridge. The building is brown brick with white stone trim and a red tile roof, with structural steel girders and concrete reinforcement.
It was used for streetcars up until 1956 and used as transit offices up until 1960. It is now used by Georgetown University for classrooms and offices.