504 (MBTA bus)

GREEN LINE "A" BRANCH Watertown Line
An "A" Branch trolley on Cambridge Street in 1968
Overview
Type	Light rail
System	Green Line
Status	closed and abandoned
Locale	Boston and Watertown
Termini	Park Street Station, Boston Watertown Yard
Operation
Opened	1856 (first sections, as part of Cambridge Horse Railroad) 1889 (electrification on route from Oak Square to Boston)
Closed	June 20, 1969
Operator(s)	Various private companies, then M.T.A., then MBTA
Character	Underground from Park Street to Kenmore, central median from Kenmore to Packards Corner, street-running from Packards Corner to Watertown Yard
Rolling stock	PCC streetcars (1941-1969)
Technical
Number of tracks	2
Track gauge	4 ft 8 1⁄2 in (1,435 mm)
Route map to Lechmere Park Street Boylston Pleasant Street Incline Copley "E" Branch Hynes Convention Center Kenmore "D" Branch "C" Branch Blandford Street Portal Blandford Street Boston University East Boston University Central Boston University West St. Paul Street Pleasant Street Braves Field Loop closed 1962 Babcock Street "B" Branch Packards Corner Street-running stops Union Square Street-running stops Oak Square Oak Square Loop Street-running stops Newton Corner Street-running stops Watertown Yard This diagram:

The "A" Branch or Watertown Branch was a streetcar line in the Boston, Massachusetts area, operating as a branch of the Massachusetts Bay Transportation Authority Green Line. In 1969 it was replaced by the 57 bus, though the tracks remained continuous until March 1994.

The line started as a horse car street railway, as a branch of the Cambridge Horse Railroad. The branch split at Central Square, Cambridge, and crossed the Charles River on the River Street Bridge into Allston. It continued on through Union Square, and in 1858 was opened to Oak Square in the center of Brighton. The part east of Union Square later became part of the 64 bus route.

The first electric trolleys in Boston ran between the Allston Carhouse (northeast of Union Square) and Park Square downtown, on tracks running south on Harvard Street, east on Beacon Street, south on Massachusetts Avenue, and east on Boylston Street. These first ran on January 1, 1889, on tracks that had been built for horse cars.

On June 13, 1896, tracks opened from Union Square east along North Beacon Street and Commonwealth Avenue to Kenmore Square, merging with the existing tracks on Beacon Street. That year, the western terminal was also extended to just shy of Newton Corner, with Newton Corner service beginning May 21, 1898. On December 9, 1912, the route was extended north to Watertown on tracks that had been used by routes from Cambridge to Newton Corner since 1900. During the early part of the 20th century, the line was also used for light rail freight service.