New York State Route 125 (NY 125) is a north–south state highway located within Westchester County, New York, in the United States. The route begins at an intersection with U.S. Route 1 (US 1) in the Town of Mamaroneck and ends at a junction with NY 22 in the city of White Plains. A section of the route in the city of White Plains is maintained by Westchester County and co-designated as County Route 26 (CR 26). A second county-owned segment exists along the New Rochelle–Scarsdale line as County Route 129. Both numbers are unsigned. NY 125 was assigned as part of the 1930 renumbering of state highways in New York, initially extending from US 1 to Mamaroneck Avenue in White Plains. It was extended north to NY 22 in the mid-1930s. Route description NY 125 begins at an intersection with US 1 (Boston Post Road) in the town of Mamaroneck. Proceeding northwest as Weaver Street, NY 125 crosses through a residential section of Mamaroneck as a two-lane local road. It crosses over the New England Thruway (I-95) and the Metro-North Railroad's New Haven Line (shared with Amtrak as its Northeast Corridor) before bending southward around a school and climbing into the residential neighborhoods overlooking Mamaroneck. Passing Bonnie-Briar Country Club, the route crosses the Sheldrake River and turns northward to run along the border between the city of New Rochelle and the village of Scarsdale. After exiting Mamaroneck, the route becomes county-maintained and co-designated as CR 129. It briefly runs along the eastern edge of New Rochelle's Pinebrook Heights and Pinebrook neighborhoods ahead of an interchange with the Hutchinson River Parkway (exit 20) in the Quaker Ridge section of New Rochelle. Access to the Parkway northbound is via Hutchinson Avenue while southbound access is provided via Stratton Road and Pinebrook Boulevard. County maintenance ends just south of the junction while NY 125 continues past the parkway along the New Rochelle–Scarsdale line. It serves residential parts of both communities prior to fully entering Scarsdale and accessing the Heathcote section of the village. Here, the route connects to the west end of the Heathcote Bypass, a two-lane highway running below grade along the northern edge of the neighborhood. The bypass is designated County Route 143 and signed as NY 125 Bypass. NY 125 continues directly into the center of Heathcote, where it turns northeast onto Palmer Avenue at an intersection known locally