501 (MBTA bus)
| Company type | Streetcar route |
|---|---|
| Industry | Public transportation |
| Founded | 1858 |
| Defunct | 1969-06-20 |
| Fate | Replaced by MBTA bus route 57 |
| Headquarters | Boston , United States |
Area served | Boston metropolitan area |
| Products | Streetcar transit service |
The A branch, also known as the Watertown Line, was a streetcar route in the Boston metropolitan area, functioning as an extension of the Massachusetts Bay Transportation Authority (MBTA) Green Line. This line connected Watertown to Kenmore Square by way of Newton Corner, Brighton, and Allston, then continued through the Boylston Street and Tremont Street subways to reach Park Street station.
Segments of this route have their origins in horse-drawn streetcar lines established between 1858 and 1880. The portion linking Union Square to Oak Square was electrified in 1889 as part of the Beacon Street corridor. By 1896, electric streetcar services linked Newton Corner (also known as Nonantum Square) with downtown Boston via Brighton and Watertown. Service through Brighton was extended to Watertown in 1912. The line remained operational until June 20, 1969, when it was supplanted by MBTA bus route 57; however, non-revenue trips to Watertown Yard persisted until 1994.
Origins
The Brighton Horse Railroad, a horsecar street railway system, began construction in 1858. It originated at Central Square in Cambridge, crossed the Charles River into Allston, and proceeded through Union Square along Cambridge and Washington Streets, terminating at Oak Square in Brighton. Managed by the Union Street Railway—a holding company affiliated with the Cambridge Railroad—the line commenced operations on November 15, 1858, following resolution of a conflict with the Boston and Worcester Railroad concerning track crossings. By April 1878, service frequency had doubled to intervals of thirty minutes. In 1880, a second route connecting Brighton to Cambridge opened via Market Street and Western Avenue. Although an extension from Oak Square to Nonantum Square was planned, it was never constructed; instead, a separate line connecting Watertown to Nonantum Square was established.
During the late 1880s, the West End Street Railway consolidated several horsecar lines including the Cambridge Railroad. On January 3, 1889, West End inaugurated its first electric streetcar service between Allston Carhouse (located north of Union Square) and Park Square, traveling along Harvard Street, Beacon Street, Massachusetts Avenue, and Boylston Street. Electric operations were extended to Oak Square on January 13. Electric service from Watertown to Mount Auburn commenced on December 12, 1893; double-tracking followed later that decade. On August 18, 1896, the Western Avenue line became double-tracked and electrified—marking the final horse-drawn car route over the West Boston Bridge to be converted.
Tracks opened on May 18, 1896 from Union Square eastward along North Beacon Street and Commonwealth Avenue reaching Kenmore Square, linking with existing Beacon Street tracks. By June 13 of that year, service extended westward nearly reaching Newton Corner (Nonantum Square). Starting November 8, 1897, Newton-bound service via Commonwealth Avenue began operating through the Tremont Street subway. A longer route from Nonantum Square to City Point via Allston and Coolidge Corner was introduced on August 4, 1900. On December 9, 1912, service expanded northward to Watertown utilizing preexisting Galen Street trackage. In addition to passenger transport during the early twentieth century, this line also accommodated freight operations.
The Boylston Street subway reached Kenmore Square on October 3, 1914; following this development, Watertown-bound service via Brighton Center immediately transitioned into this tunnel. In mid-1915, high-capacity center-entrance streetcars were introduced as trailers on the Watertown Line—the first implementation of such vehicles within the BERy system. Evening peak short-turn trips from Oak Square were extended to Watertown beginning February 23, 1922. The Blandford Street portal along Commonwealth Avenue just west of Kenmore opened on October 23, 1932—representing the last significant alteration to the route. In 1941, this line became Boston’s first to feature primary PCC streetcar service replacing earlier vehicle models.
North Beacon Street line
In June 1894, the West End requested municipal authorization to establish a streetcar route along North Beacon Street, stretching from Union Square to the Watertown boundary. Shortly thereafter, the Newtonville and Watertown Street Railway obtained permission to build the segment between and Union Square, intending to utilize West End tracks for access to downtown Boston. Despite opposition from the West End, the Watertown Arsenal granted approval in 1896, leading to the line’s construction in 1898.
After operational disagreements arose between its parent company, Newton and Boston Street Railway, and the BERy, the line commenced service in 1900. On November 18 of that year, through service linking Watertown with the Tremont Street subway began as a branch of the Newton-Brighton line. The BERy assumed control from Newton and Boston in 1907. It is noteworthy that the segment west of Market Street remained single-tracked, which was unusual among BERy-operated routes.
The Newton Street Railway, later known as the Middlesex and Boston Street Railway, initiated Waltham–Park Street service via North Beacon Street on February 23, 1903. This route was redirected to Central Square by April 27, 1912, thereby diverting away from North Beacon Street. Similarly, Oak Square–Boston service experienced gradual reductions. Watertown–Park Street operations along North Beacon Street continued until October 1914; following the Boylston Street subway’s opening, service was curtailed to a shuttle running between Watertown and Union Square. By June 2, 1917, this shuttle was further shortened to operate solely between the North Beacon Street bridge and Union Square.
On February 23, 1922, bus service replaced the shuttle. A short-lived Watertown–Arsenal Street bridge bus operated during 1925–26. In December 1925, the Central Square–Union Square route was rerouted via Western Avenue and Soldiers Field Road alongside a newly introduced River Street bus route, which extended to Union Square by September 1926, supplanting streetcar service. These routes were consolidated in February 1933 to eliminate transfers; today, this corridor is served by the route 64 bus.
Closure
Prior to 1967, the Watertown Line was identified as route 69; its present number, 57, originally applied to short-turn trips on the Huntington Avenue line terminating at Heath Street. The line carried the letter designation "A" as the northernmost branch of the Green Line. Turnaround loops were located at Union Square, Oak Square, and at Watertown’s terminus. Additionally, from 1915 until 1962, a loop operated at Braves Field for special event services along Commonwealth Avenue.
The inauguration of the Riverside Line in 1959 resulted in Cambridge streetcar routes converting to trackless trolley operation, thereby releasing PCC streetcars for deployment on Riverside. However, by the late 1960s, an aging fleet primarily composed of 1940s PCC cars combined with a heterogeneous vehicle mix complicated maintenance efforts. Due to vehicle shortages and operational challenges, MBTA opted for a trial closure of the A branch. The decision was influenced by extensive street running between Watertown and Packards Corner and previous resistance to extending service beyond Newton Corner. Streetcar operations ended on June 20, 1969; bus service under route number 57 commenced immediately thereafter.
Track removal
Following cessation of service, tracks remained intact to maintain access to Watertown Carhouse for maintenance purposes. The final use occurred in 1993 when PCC streetcars destined for refurbishment on the Ashmont–Mattapan High-Speed Line utilized this facility. Overhead wiring was dismantled in March 1994.
By summer 1996, most overhead equipment and rails were removed during resurfacing work on North Beacon Street. Some remnants endure within the Watertown Yard bus terminal and as a short stub track at Packard's Corner—once employed for storing disabled trains until it was shortened in the mid-2000s; this switch was disconnected in 2014 and subsequently paved over by 2020.
Proposals to restore service aimed at providing a direct downtown connection from this northern corridor without requiring transfers at Kenmore were ultimately rejected due to high costs and safety concerns compared with existing bus operations.
Route 57
The 57 Watertown Yard–Kenmore station bus service originated in 1969 as a successor to the A branch streetcar line. It largely traces the same corridor, except at the Newton Corner rotary where inbound buses follow regular traffic flow instead of using a counterflow lane. Initially, the 57 operated as a limited-stop service between Packards Corner and Kenmore station to supplement the "B" branch local service; however, starting in December 2006, it began serving all local stops along Commonwealth Avenue.
Following the elimination of free transfers in 1961, passengers traveling from Watertown had to pay double fares until January 2007, when a revised fare system reintroduced free transfers via the CharlieCard.
Short-turn trips running between Oak Square and Kenmore were discontinued in 1971 but were partially reinstated in later years. To alleviate crowding during weekday peak periods, the MBTA introduced the 57A Oak Square–Kenmore short-turn service in September 2008. Around half of the peak trips operated as 57A, while off-peak buses continued along the full route. The Oak Square short-turn service was discontinued in December 2020 except for limited school-day runs, with increased frequency maintained on the full route.
Route 57 remains a crucial MBTA bus corridor, maintaining steady intervals of 10–12 minutes and ranking among the busiest routes with over 10,000 average weekday boardings recorded in 2012. Weekday operations are based out of the Albany Street Bus Facility, while evening and weekend services operate from Cabot Garage. An early morning trip to , internally designated as route 191 but publicly shown as route 57, serves both MBTA personnel and general riders.
An MBTA review conducted in 2018–19 highlighted peak-time overcrowding and reliability challenges on route 57 but did not recommend immediate modifications. The bus network redesign proposed in 2022 suggested increasing frequency to at least every 15 minutes throughout service hours. The 57A short-turn was briefly reinstated in December 2024 but was discontinued again by April 2025.
Express buses
Two express bus routes serve areas west of Brighton Center, providing service to downtown Boston via Copley Square:
- 501 Brighton Center–Federal Street & Franklin Street
- 504 Watertown Yard–Federal Street & Franklin Street
Express transit service originating from Brighton and Watertown began during the operational period of the "A" branch streetcar. The initial route, numbered 61, launched in July 1967 and underwent several renumberings before evolving into today's routes 501 and 504. Significant changes included routing adjustments through Newton Corner and Union Square, with express designations incorporated into the assigned 300-series numbers starting June 1970.
Throughout the 1970s and 1980s, these express routes experienced minor changes to their downtown routing patterns. Midday and Saturday services were expanded on route 302 in the early 1980s; this route was later renumbered to 304. The current numbering system—routes 501 through 504—was established in September 1996, with route 503 added in January 2005.
An MBTA system review from 2018–19 identified challenges on routes 501 and 503 such as closely spaced stops, irregular afternoon schedules, and reliability concerns; no significant issues were found on routes 502 and 504. To enhance operational efficiency, outbound buses on routes 502 and 504 were rerouted to bypass the Newton Corner rotary loop starting September 2019; simultaneously, outbound buses on routes 501 and 503 began serving stops at Newton Corner.
During the COVID-19 pandemic, weekday-only routes (502 and 503) were suspended while routes 501 and 504 operated on reduced schedules beginning March 2020. Route 504 assumed most of route 502’s service pattern by running via Copley Square on most trips. Route 501 was temporarily suspended between June and August 2020 before resuming service with trips extending to Copley Square.
The May 2022 network proposals aimed to make these pandemic-related adjustments permanent by restricting routes 501 and 504 to weekday peak periods only. However, an update in November 2022 reinstated midday service on route 504.