The M101, M102 and M103 bus routes run southbound on Lexington Avenue north of East 24th Street.

[8] The M103 begins its route at City Hall and travels north via Park Row and the Bowery.

At Astor Place, it continues north alongside the M101 and M102 along Third to East 125th Street, where it terminates.

In 1941, Surface Transportation Corporation began operating former Third Avenue Railway routes.

[12] On July 17, 1960, Third Avenue north of 24th Street became one-way northbound, and southbound buses were moved to Lexington Avenue, and the two parallel bus lines were combined as a one-way pair, keeping the route number M101.

[13] After a strike in 1962, the entire Fifth Avenue system was transferred to the newly formed Manhattan and Bronx Surface Transit Operating Authority on March 22, 1962.

The route was designed to keep the number of stops to a minimum to attract ridership.

[21] Limited-stop service on the M101 began on October 14, 1991, with alternate buses running limited between 7 a.m. and 7 p.m.[22] On September 10, 1995, the M103 was created to improve reliability along Third and Lexington Avenues, curtailing the M101 and M102 south of Astor Place.

At the same time, southbound M98 service into the George Washington Bus Terminal was discontinued.