Blue Line (MBTA)

The Blue Line is a rapid transit line of the Massachusetts Bay Transportation Authority (MBTA) in Boston, Massachusetts. It is the shortest of the MBTA's four subway lines, running approximately 6 miles (9.7 km) from Bowdoin station in downtown Boston to Wonderland station in Revere. It is the only MBTA subway line to operate entirely underground or at ground level, without any elevated sections.

Primarily serving the northern portions of downtown Boston, East Boston, and Revere, the Blue Line offers connections to Logan International Airport via the Airport station, where passengers can transfer to Massport's free shuttle buses. It also provides access to the Government Center area, with transfers to the Green Line and connections to the Red Line (via Park Street or State Street).

The Blue Line is unique in the MBTA system for its use of narrower subway cars compared to the other lines. This design choice was largely influenced by the historic street layout in downtown Boston, where tight curves and narrower tunnels were required for the initial construction of the line.

Historically, the Blue Line began as part of the East Boston Tunnel, initially built for streetcars in 1904. It was gradually converted to rapid transit operation, with the final streetcar service ending in 1952. Extensions have been added over time, including the branch to Wonderland, completing the current alignment. Future extensions to Lynn have been proposed but have not yet been implemented.