The Orange Line, originally the Main Line Elevated, connects Oak Grove in Malden to Forest Hills in Jamaica Plain. The downtown tunnel segment, under Washington St., runs from Essex Street (Chinatown) to North Station, and was constructed in the early 1900s after several years of elevated cars running into the Tremont Street subway (today's Green Line). The original elevated ran over Washington Street from Arborway to Everett, with a loop (largely over Atlantic Ave.) between the South End and North station; in the 1970s, the Haymarket–North Extension took over most of the B&M Western Route between North station and Melrose, after which the elevated in Charlestown and Everett was demolished. In 1987, the Southwest Corridor Extension branched off of the existing tunnel south of Chinatown for new stations at Tufts Medical Center and Back Bay, then running parallel to the MBTA/Amtrak Providence Line to Forest Hills; as with the northern extension, the Washington St. elevated was then demolished.