The M1, M2, M3, and M4 are four local bus routes that operate along the one-way pair of Madison and Fifth Avenues in the borough of Manhattan in New York City between Greenwich Village and Harlem.

[6] During weekdays, every other southbound trip terminates in East Village, Manhattan, using 8th Street (St. Marks Place) to travel between 5th and 4th Avenues.

[7] The M2 also has a limited-stop variant, making limited stops south of 110th Street with no local service during the daytime.

Buses were substituted for streetcars by the Madison Avenue Coach Company in March 1936.

The Madison Avenue Coach Company, a New York Railways subsidiary,[20] started operating replacement buses on February 1, 1935.

[23] The path of the 1 and 2 south of Union Square was changed on November 10, 1963, to use Broadway rather than Fourth Avenue and Lafayette Street, due to Lafayette Street becoming one-way northbound and Broadway becoming one-way southbound.

[24] On that same day, the southern terminus for FACCo's 2 and 3 was moved to 8th Street and Fourth Avenue,[25] after terminating the prior two months at 8th Street between Fifth Avenue and University Place following a ban on all bus traffic through their prior terminus of Washington Square imposed by the city on September 2, 1963.

[30] In 1976, eight double-decker buses were placed into service on the M4 and M5 routes as part of a two-year test.

[31] The buses were 14.5 feet (4.4 m) tall, which required the relocation of several traffic lights and removal of tree limbs along the routes.

In January 2000, the MTA Board announced plans to implement limited-stop M2 service on Sundays between 10 a.m. and 6 p.m. due to continued increases in weekend ridership.

At the time, northbound buses ran via Broadway and West 168th Street before turning north onto Fort Washington Avenue, while southbound buses ran via Fort Washington Avenue before turning south onto Broadway.

The change would be made to eliminate the M4's asymmetric route and reroute it from a congested block of West 168th Street.

The revised changes would eliminate the u-turn and, by having southbound M18 buses share a stop with the M2 and M3 at Broadway and West 168th Street, could potentially equalize boarding on those routes.

[36] Plans were announced in April 2002 to reroute northbound evening and late night M2 service off of Wanamaker Place, University Place, and East 14th Street and onto Fourth Avenue, which was the route used by M2 during the rest of the day.

After numerous requests to rescind some of the 2010 service cuts, the MTA restored the M1 to 8th Street on the weekends on January 6, 2013.

[41] There was a proposal underway to re-extend this line back down to Worth Street in early 2017.

[42] The M1 was extended back down to Grand Street on September 3, 2017, though downtown buses run on Broadway.

This was due to a street-widening along 32nd Street that would cause delays for M4 buses from terminating there, since that portion of the route was shared with the Q32, which continues northward from Penn Station to Jackson Heights, Queens.

[43] To allow M4 riders to access Penn Station, and vice versa, free transfers would be available between Q32 and M4 buses going in the same direction.

[44] However, the plan was then changed to have the M4 continue down to 32nd Street, where it would terminate midway between 5th and Madison Avenues, two blocks from Penn Station.