- Western Terminus:
- South Riverside Avenue (NY 9A) in Croton-on-Hudson
- Eastern Terminus:
- Saw Mill River Road (NY 118) in Yorktown Heights
- 7.75 miles
NY 129 is an east/west route extending from Croton-on-Hudson to Yorktown Heights. It begins at South Riverside Avenue (NY 9A) near where it splits off from the Croton Expressway (US 9) in Croton-on-Hudson. It runs northeast to Croton Gorge Park, where the New Croton Dam is located. From there, it runs east along the north side of the New Croton Reservoir. It passes under the Taconic Parkway, but there is no interchange. Shortly thereafter, it ends at Saw Mill River Road (NY 118) in Yorktown Heights. The entire length of NY 129 is a two-lane undivided road.