The route was once operated by the now defunct Hudson Pier Depot and was known only as the M14. When the depot was taken over by the Quill depot, it was separated into three lines, the M14A, M14C and M14D. After the 9/11 attacks, the block of 14th Street between Avenue C and Avenue D was closed to the public, forcing the M14D to run the M14C route, eventually it was decided since the route ran primarily on Avenue D the route would be renamed M14D. From 2004 to 2006, the M14C briefly returned running down Avenue C to Houston Street then turning East towards Avenue D/Columbia Street and resuming the normal route. This new route began running late and caused confusion with the M21 on Avenue C and eventually service returned to its current state as the M14A and M14D. Afterward, Avenue C was temporarily served by the M21 bus, but since 2010, it has been served by the M9 bus.