Blue Line (MBTA)

The Blue Line is a rapid transit line in the Greater Boston metropolitan area, one of four rapid transit lines operated by the Massachusetts Bay Transportation Authority (MBTA). It runs from Bowdoin station in downtown Boston under Boston Harbor to East Boston and Revere on the inner North Shore, where it terminates at Wonderland. The stop at Airport Station, by way of a free shuttle bus, is one of two rapid transit connections to Logan International Airport. In 1967, during a systemwide rebranding, the line was assigned the blue color because it passes under the Boston Harbor. With an end-to-end travel time of less than twenty minutes, the Blue Line is the shortest of Boston's heavy-rail lines and the only line to have both third rail and overhead catenary sections.

The East Boston Tunnel was built as a streetcar tunnel in 1904 with Howard A. Carson as chief engineer; after an extension to Bowdoin in 1916, it was converted to heavy rail metro rolling stock in 1924. In 1952 and 1954 the line was extended along the former route of the Boston, Revere Beach and Lynn Railroad, in a project intended to reach Lynn but ultimately cut short to Wonderland. Further extensions to Lynn and Charles/MGH downtown are long-planned but not yet funded. From approximately 1998–2011, the MBTA made most Blue Line stations fully accessible as part of a larger effort to accommodate 6-car trains on the line. As of 2018, the only station in service on the Blue Line which is not fully accessible is the downtown Boston terminus Bowdoin.