As with many large cities, a large number of Boston-area streetcar lines once existed, and many continued operating into the 1950s. However, only a few now remain, namely the four branches of the Green Line and the Ashmont–Mattapan High-Speed Line, with only one (the Green Line E branch) running regular service on an undivided street. History The first streetcar line in the Boston area was a horse-drawn line from Central Square, Cambridge to Bowdoin Square, Boston opened by the Cambridge Railroad on March 26, 1856. Over the following decade a large number of horsecar lines were built by different companies, including the Metropolitan Railroad, Middlesex Railroad, and South Boston Railroad; these companies competed with each other while also sharing tracks in many locations. By the mid-1860s horsecar lines reached to Lynn, Arlington, Watertown, Newton, West Roxbury, and Milton. In 1887 the various Boston-area horsecar companies (except for the Lynn and Boston Railroad) were all consolidated into the West End Street Railway. In 1889 the West End Street Railway experimented with electric power for its streetcars; the results were so promising that it abandoned a cable car project already under construction. Several lines were electrified in 1889 and by 1895 almost the entire system had been electrified. The last horsecar line was abandoned in 1900. In 1897 the recently-formed Boston Elevated Railway (BERy) took over the West End Street Railway in order to make the streetcar lines part of its planned rapid transit system. In 1897 the Tremont Street Subway opened and many streetcar routes that had previously used surface tracks in downtown Boston were rerouted into the subway. Over the following decades the opening elevated and underground rapid transit lines (which became today's Orange Line and Red Line), as well as extensions of the Tremont Street subway (which became the Green Line), allowed progressively more streetcar lines to be removed from the congested streets downtown and rerouted to rapid transit stations further out. Passengers could transfer for free between streetcars and rapid transit lines to complete their journeys to or from downtown. In 1904 the East Boston Tunnel opened and was initially used to allow streetcars from East Boston to reach downtown, but in 1924 it was converted into another rapid transit line (part of today's Blue Line) operated with free transfers to and from streetcars at Maverick station. In the 1920s as competition from cars increased and bus technology