The M Queens Boulevard Local or the M 6 Avenue Local or the M Myrtle Avenue Local is a service of the New York City Subway. It is colored orange on the route sign (either on the front and/or side - depending on equipment used) and on station signs and the NYC Subway map, as it represents a service provided on the IND 6th Avenue Line in Manhattan. The M runs at all times. During late nights and weekends, it runs as a shuttle from Metropolitan Avenue in Middle Village, Queens, to Myrtle Avenue in Brooklyn. During middays, it is extended to Forest Hills-71st/Continental Avs weekdays, and becomes the only line to use the connection from the Chrystie St Tunnel after Delancey St-Essex St to 6th Av/53rd St Line to the Queens Blv. Tunnel. Service is always fully local, although, on occasion, when an M train is running late, or if another train is following close behind, it will run express, stopping at only the major stations, which include Myrtle Avenue, Wyckoff Avenue, and Fresh Pond Road.
In 1924, BMT assigned numbers to its services. The BMT Myrtle Avenue Line had two services, the Myrtle Avenue-Forest Hills-71st Av Line (10) and the Myrtle Avenue Line (11). The former operated via the east half of the Myrtle Avenue Line (the only part remaining) and the BMT Broadway–Queens Blvd Line to end at Forest Hills-71st Av; the latter stayed on the Myrtle Avenue Line all the way to its end at the Forest Hills, operating over the tunnel to Forest Hills-71st Av in Queens.
10 trains ran only from 06:00 to 20:00 on weekdays, 06:00 to 21:00 on Saturdays, and 12:30 to 23:00 Sundays. During morning rush hours, they ran express from Central Avenue to Essex Street; evening rush hour trains ran express from Bowery to Myrtle Avenue. At other times, trains ran local and passengers could transfer between 11 and 14 or 15 trains at Myrtle Avenue.
Between 1925 and 1931, service was changed so express trains in both directions ran express between Essex Street and Myrtle Avenue. Sunday trains were removed in June 1933; also between 1931 and 1937 11 trains stopped running over the Brooklyn Bridge, instead ending at Sands Street on the Brooklyn side.
Saturday express 10 service was cut on June 28, 1952, and all non-rush hour service was cut June 28, 1958. By 1959 the service was being advertised as Myrtle (Chambers) express service, compared to Myrtle (Jay) local service via the 11 (Bridge Street had been renamed to Bridge–Jay Streets).
In 1960, the letters M and MJ were assigned to 10 and 11 service, respectively; it is probable that MJ stood for Myrtle (Jay). MJ was only marked on maps and station signs; the cars along that route never had signed designations. Since the new cars using letter designations were not yet running on the Myrtle-Chambers service, it remained designated as 10; while M was used to designate rush hour Nassau Street specials on the Brighton and Fourth Avenue Lines. With the opening of the IND Chrystie Street Connection on November 26, 1967, the new letters officially redesignated the 10 and 11 services on maps and signs.
On February 23, 1960, peak direction 10 trains began to stop at Marcy Avenue, which had been a local stop. On July 1, 1968, M service was extended two stations in Manhattan to end at Broad Street. Around this time, an Template:NYCS MM service was proposed, which would have run to 57th Street via the IND Sixth Avenue Line, but this never materialized. It was included on some rollsigns printed at the time. The west half of the Myrtle Avenue Line was closed on October 3, 1969, ending MJ service, and SS shuttle service was begun east of Myrtle Avenue.
The distinct shuttle service was gone by 1972, leaving only M service on the Myrtle Avenue Line. During normal hours (06:00 to 20:00) it not only ran to Manhattan, but extended through the Montague Street Tunnel and along the BMT Brighton Line to Stillwell Avenue. At other times, it simply served as a shuttle to Myrtle Avenue.
On August 27, 1976, the M changed from the Myrtle Avenue Express to the Myrtle Avenue Local, no longer running express at all, due to the end of K service.
On April 26, 1986, the south Brooklyn terminal was moved to 95th Street (running express on the BMT Fourth Avenue Line), and in 1987, it was moved again to use the BMT West End Line. Midday, it ran to Ninth Avenue and during rush hours, it was extended to Bay Parkway.
In 1994 the M became local along Fourth Avenue, while the N shifted to express.
In April 1995, midday service was cut back to Chambers Street to make room for Q trains on the Montague Street Tunnel due to the reconstruction of the Manhattan Bridge's north side; it was then that M service took its current form.
The Williamsburg Bridge was closed between April 30 and September 1, 1999, cutting M service in two. At all hours, the north half ran from Metropolitan Avenue to Marcy Avenue, and the south half ran rush hours only from Chambers Street to Bay Parkway.
From July 23, 2001 to February 20, 2004, due to Manhattan Bridge work, M trains were extended middays and evenings until 22:00 back to Ninth Avenue, and rush hour trains ran to Bay Parkway.
Immediately after the September 11, 2001 attacks, the M ran only as a shuttle to Myrtle Avenue. On September 17, the M was extended via the BMT Sea Beach Line to Stillwell Avenue at all times, due to N service being suspended (this was the only time the M returned to Coney Island–Stillwell Avenue since April 1986). On October 28, normal service on both lines was restored.But now,M line runs from Middle Village-Metropolitan Av to Forest Hills-71st/Continental Avs on weekdays and runs shuttle from Middle Village-Metropolitan Av to Bushwick-Myrtle Av & Broadway on weekends and late nights (midnight to 6 AM).