NY 127 begins at an intersection with
US 1 (East Boston Post Road) in the village of
Mamaroneck. The highway proceeds northeast through Mamaroneck as a two-lane residential street named Keeler Avenue, crossing through the Old Rye Neck neighborhood. The route soon reaches a junction with Harrison Avenue, where it turns north off Keeler, leaving the Old Rye Neck neighborhood and soon the entire village. Now in the town and village of
Harrison, NY 127 continues as Harrison Avenue, bending north into downtown Harrison, as a two-lane commercial street. Just after the junction with Halstead Avenue, the route crosses west of the parking lot for the
Harrison Metro-North Railroad station and soon over the
New Haven Line (
Northeast Corridor) tracks. After crossing the railroad, NY 127 enters a residential section of Harrison, crossing north as Harrison Avenue. Soon the route crosses under, but does not interchange with, the
New England Thruway (
I-95), winding northeast past the Harrison Avenue School and a junction with Union Avenue (unsigned
CR 94). The route makes a gradual bend to the north, passing west of the Willow Ridge Country Club near the intersection with North Street. At the intersection, NY 127 drops the Harrison Avenue moniker, gaining the North Street one. The route bends northwest through a residential section of Harrison, reaching a junction with the
Hutchinson River Parkway (exit 14). Upon crossing the Hutchinson River Parkway, NY 127 enters the Rosedale section of the city of
White Plains. as it passes the Maple Moor Golf Course. Winding up the hills of White Plains, the route crosses through the North Street section, becoming a four-lane residential street past
White Plains Senior High School. Passing a commercial complex, NY 127 turns north and enters an interchange with the Cross Westchester Expressway (
I-287). This interchange, which also serves Westchester Avenue (
CR 62), marks the northern terminus of NY 127, whose right-of-way continues through the town of Harrison as White Plains Avenue. ==History==