The Fourth and Madison Avenues Line is a public transit line in Manhattan, New York City, United States, running mostly along Park Avenue and Madison Avenue from Lower Manhattan to Harlem. Originally a streetcar line, it is now much of the M1 bus route, operated by the New York City Transit Authority. The M1 bus now runs southbound on Fifth Avenue rather than Madison Avenue north of 40th Street.
The New York and Harlem Railroad was the first railroad in Manhattan, opening from City Hall north along Centre Street, Broome Street (northbound trains were later moved to Grand Street), the Bowery, Fourth Avenue, and Park Avenue to Harlem in the 1830s, and was extended southwest along Park Row to Broadway in 1852. A branch opened along 42nd Street and Madison Avenue to 73rd Street in 1870, and the NY&H began to operate streetcars along this route; it was later extended to Harlem. Buses were substituted for streetcars by the Madison Avenue Coach Company in March 1936. The New York City Omnibus Corporation took over operations in 1951, and changed its name to Fifth Avenue Coach Lines in 1956; the Manhattan and Bronx Surface Transit Operating Authority took over operations in 1962.
When the bus that replaced the Lexington and Lenox Avenues Line was terminated, the Madison Avenue bus was extended west on 139th Street and north on Lenox Avenue to 147th Street. When Madison Avenue became one-way northbound, southbound traffic was moved to Fifth Avenue, replacing the original route of the Fifth Avenue Coach Company.