[a] The N was originally the Brooklyn–Manhattan Transit Corporation's 4 service, running along the BMT Sea Beach Line to the Manhattan Bridge.

Originally, it used the south tracks of the Manhattan Bridge, which at that time connected to the BMT Nassau Street Line.

[11] On September 4, 1917, the first part of the BMT Broadway Line and the north side tracks of the Manhattan Bridge opened.

[11] Weekday and Saturday summer trains leaving Coney Island between 6:37 a.m. and 8:37 p.m. began running non-stop between Kings Highway and 59th Street on August 1, 1920.

[11] On May 2, 1957, service was extended north via the express tracks from Times Square to 57th Street–Seventh Avenue, and trains stopped bypassing 36th Street during the AM rush hour.

In addition, on weekday and Saturday evenings, late nights, and all day Sundays, they ran local on the BMT Fourth Avenue Line.

This short-lived service began on November 27, 1967 (with the opening of the Chrystie Street Connection)[13] and ended April 12, 1968, due to low ridership.

[11] On August 30, 1976, weekday N service was extended north over the BMT 60th Street Tunnel Connection to Forest Hills–71st Avenue to replace the discontinued EE.

[11] On January 24, 1977, as part of a series of NYCTA service cuts to save $13 million, many subway lines began running shorter trains during middays.

As part of the change, N trains began running with four cars between 9:30 a.m. and 2:15 p.m.[16] On August 27, 1977, N service was cut back during late nights, only operating between 36th Street and Coney Island.

Because of the large amount of train traffic now running on those tracks, rush hour and midday N service was rerouted via the Montague Street Tunnel, making local stops in Manhattan and Brooklyn, though evening, night and weekend trains continued to use the bridge and express tracks in Brooklyn.

[18] As part of the New York City Transit Authority's proposed service plan to serve the new Archer Avenue Line upper level, the N would have been extended to Jamaica Center during weekdays.

[25] This change was intended to improve the appearance and reliability of service on the R, since all trains on the Astoria and Broadway Lines were part of the graffiti-free program.

[18] The Transit Authority and politicians pressured the New York State Department of Transportation to resume N train service on the bridge's south side on September 30, 1990, despite warnings from engineers that the structure was unsafe and major repairs still had to be made.

Trains ran express on Broadway in Manhattan (stopping at 49th Street) and Fourth Avenue in Brooklyn at all times except late nights (10 p.m. to 5 a.m.).

[18] On December 27, state inspectors forced N service to be rerouted via the Montague Street Tunnel again after discovery of corroded support beams and missing steel plates, running local on its entire route at all times.

[9] From April 30, 1995, to November 12, 1995, the north side of the Manhattan Bridge was closed during weekday midday and weekends for structural repairs.

Midday N service ran local in Brooklyn, replacing the M, which was cut back from 9th Avenue to Chambers Street.

[38] On September 8, 2002, because of the ongoing reconstruction of Coney Island terminal, weekend and late night N service was reduced to a shuttle between 86th and Pacific Streets, running express on the BMT Fourth Avenue Line.

In its place, the W was extended to Manhattan and Astoria, Queens at all times; this was because the W was the only route still serving Stillwell Avenue during this part of the reconstruction.

[9][43] On June 28, 2010, the N began running local in Manhattan north of Canal Street at all times, replacing the W on weekdays which was discontinued due to budget problems, effectively adopting the weekend service pattern.

[64][65] The N began running local in Manhattan in March 2020 after the W was temporarily suspended due to the COVID-19 pandemic;[66] regular N and W service was restored in June.