Green Line E branch

The E branch (also referred to as the Huntington Avenue branch, or formerly as the Arborway Line) is a light rail line in Boston, Cambridge, Medford, and Somerville, Massachusetts, operating as part of the Massachusetts Bay Transportation Authority (MBTA) Green Line. The line runs in mixed traffic on South Huntington Avenue and Huntington Avenue between Heath Street and Brigham Circle (the last MBTA street-running tracks in revenue service), in the median of Huntington Avenue to Northeastern University, then into the Huntington Avenue subway. The line merges into the Boylston Street subway just west of Copley, running to North Station via the Tremont Street subway. It then follows the Lechmere Viaduct to Lechmere, then the Medford Branch to Medford/​Tufts. As of February 2023^[update], service operates on eight-minute headways at weekday peak hours and eight to nine-minute headways at other times, using 13 to 17 trains (26 to 34 light rail vehicles).

Horsecar service on Centre and South streets in Jamaica Plain began in 1857, followed by service on Tremont Street (part of which became the west part of Huntington Avenue) to Brookline Village in 1859 and on the east part of Huntington Avenue in 1881–84. Jamaica Plain service was electrified in 1891, and Huntington Avenue service in 1894. Several branches of the Huntington Avenue line were opened west of Brookline Village between 1894 and 1900; both Huntington Avenue and Jamaica Plain service began using the new Tremont Street subway in 1897. A connector on South Huntington Avenue opened in 1903, allowing service to Jamaica Plain via Huntington Avenue. In the 1920s, Jamaica Plain service was extended to Arborway, while the western branches were reconfigured; they were cut in the 1930s.

The Huntington Avenue subway opened in 1941, cutting travel times through congested Copley Square. Ownership passed from the Boston Elevated Railway to the Metropolitan Transit Authority in 1947, and to the MBTA in 1964. Tremont Street subway service was designated as the Green Line in 1965, with the Huntington Avenue line becoming the E branch in 1967. Service was modified numerous times during the early MBTA era, including a major reconstruction of the line in 1980–82. In 1985, service past Brigham Circle was replaced with the route 39 bus – a "temporary" change that controversially became permanent, although service as far as Heath Street was restored in 1989 after replacement of the street trackage on Huntington Ave. The downtown terminal of the E branch underwent a number of changes during the MBTA era; from 1987 to 2020, it was usually Lechmere. In May 2020, the E branch was cut back to North Station for construction of the Green Line Extension, as part of which it was temporarily extended to Union Square in March 2022. It was permanently extended to Medford/Tufts in December 2022.

What became the E branch was formed from portions of several streetcar lines. The first of these was the West Roxbury Railroad, a horsecar line opened on November 14, 1857, in what was then West Roxbury. It ran from Roxbury Crossing to Jamaica Plain along Lowell Street (now Columbus Avenue), Centre Street, and South Street. The line was quickly leased by the Metropolitan Railroad, which operated through service between Jamaica Plain and downtown Boston using its line on Tremont Street. Travel time for the 4+1⁄2-mile (7.2 km)-long line was over an hour with a ten-cent fare. A two-track carhouse with a waiting room was located at the terminus of the line at Jamaica Street in Jamaica Plain. (The Metropolitan's main carhouse and barn was located at Roxbury Crossing.) In 1858, the Metropolitan opened a connector between Lowell Street and John Eliot Square, allowing Jamaica Plain cars to also use the Washington Street line (via Dudley Square) to reach downtown. The railroad also rebuilt the Jamaica Plain line that year to accommodate heavier ridership, including the double-tracking of some portions.

On August 1, 1859, the Metropolitan was granted permission to add a 1.6-mile (2.6 km)-long branch to School Street (northwest of Brookline Village) along what was then called Washington Street. (It was soon renamed as Tremont Street east of Brookline Village; the portion between Brigham Circle and Brookline Village was renamed again as part of Huntington Avenue in 1895.) The line opened on October 26, 1859. Permission to double-track the line was given on September 9, 1879. The portion west of Brookline Village may have been intermittently operated.

As the west part of the Back Bay was filled, Huntington Avenue became a major thoroughfare. The Metropolitan received rights to construct a double-track line on Huntington from Copley Square (where it connected to the existing Marlborough Street line) to West Chester Park (later renamed Massachusetts Avenue) on March 18, 1881. The 0.7-mile (1.1 km) line opened by that September, serving the exhibitions at the Mechanics Hall and New England Fair Building. A 1.2-mile (1.9 km) extension along the newly-laid-out section of Huntington from West Chester Park to Brigham Circle was granted on October 29, 1883; its opening on October 1, 1884, completed a second Brookline–Boston route. A 1.2-mile (1.9 km) branch along Longwood Avenue to Coolidge Corner opened around late 1884. Around 1888, a 0.8-mile (1.3 km) branch was opened west from Brookline Village on Boylston Street and Cypress Street, serving the Pill Hill area. (This may have been to compete with the Boston and Albany Railroad, which had begun its Newton Circuit service through Brookline in 1886.)

In November 1887, the Metropolitan was merged into the West End Street Railway as it consolidated the various Boston street railways into a unified system. After the successful electrification of the Beacon Street line in 1888–89, the West End quickly moved to electrify its entire system. The Jamaica Plain–Northern Depots line was concerted to electric operation on October 14, 1891, followed by other Tremont Street lines on October 22. The horsecar barn at Jamaica Plain was replaced with a new structure for the electric cars; in early 1901, it was in turn replaced by a 320-by-325-foot (98 m × 99 m) carhouse with a passenger waiting room and space for 150 streetcars.

The West End electrified its Huntington Avenue line in 1893–94. Work was completed by mid-July 1894 except for a short stretch near the Riverway. On August 4, all Brookline service via Huntington Avenue was converted to electric operation. This included the Washington Street branch (extended to Park Street), the Cypress Street branch, and the Tremont Street tracks to Roxbury Crossing. The Washington Street branch was extended to Beacon Street at Washington Square on September 1, allowing through service between Reservoir via Brookline Village. On August 15, 1896, an extension of the Beacon Street line opened on Chestnut Hill Avenue and Commonwealth Avenue to Lake Street. Reservoir service via Brookline Village was extended to Lake Street, where a connection was made with the Commonwealth Avenue Street Railway.