Sullivan Square station is a rapid transit station on the MBTA subway Orange Line, located adjacent to Sullivan Square in the Charlestown neighborhood of Boston, Massachusetts. It is a major transfer point for MBTA bus service, with 13 routes using a two-level busway. The station has two island platforms serving the two active Orange Line tracks plus an unused third track. The Haverhill Line and Newburyport/Rockport Line pass through the station on separate tracks but do not stop. The Boston and Maine Railroad (B&M) opened through Sullivan Square in 1845, followed by the Eastern Railroad in 1854; both railroad had stations there. The B&M acquired the Eastern in 1885 and combined their stations as part of a grade crossing elimination project in 1900–01. That station served commuter trains until 1958. The Boston Elevated Railway opened its Sullivan Square station in June 1901 as the northern terminus of the Charlestown Elevated. The massive terminal served numerous streetcar lines as well as elevated trains. The modern station opened in May 1975 as part of the Haymarket North Extension, which replaced the Charlestown Elevated; the old terminal was demolished the next year. Sullivan Square station was made accessible in the 1990s, and the busways were reconfigured in 2018–2019. Station layout Sullivan Square station is located in an open cut under the Interstate 93 viaduct just west of the Sullivan Square traffic circle. The cut has seven tracks: two freight yard tracks (Yard 21, with the tracks called 3rd Iron and 4th Iron) on the west, three Orange Line rapid transit tracks in the center, and two tracks used by MBTA Commuter Rail Haverhill Line and Newburyport/Rockport Line trains on the east. Only the west (southbound) and center (northbound) Orange Line tracks are used for revenue service; the unused east track, originally intended for express service, is only used for maintenance and testing. A pair of island platforms are located between the Orange Line tracks; the west platform serves trains in both directions, while the east platform serves only northbound trains. The platforms have a "utilitarian" concrete design similar to Community College station. A mezzanine and fare lobby above the tracks is connected to the platforms with stairs, escalators, and elevators. The entrance is from the east side of the tracks, on the upper level of the two-level busway. A passageway leads from outside the station entrance under the upper busway to the lower