At Van Cortlandt Park, NY 129 becomes residential, passing Croton-Harmon High School as it bends to the northeast.

The route continues northeast through the village, crossing an intersection with Quaker Bridge Road before becoming a wooded lane in the town of Cortlandt.

In Cortlandt, NY 129 continues north as Grand Street, paralleling a local creek and entering Croton Dam Plaza.

At the junction with Underhill Avenue, NY 129 turns southward, soon winding its way southeast under the lanes of the Taconic State Parkway, and back alongside the New Croton Reservoir.

After crossing under the Taconic,[3] the route then drops back down to the reservoir and passing a house reported to have been moved from Huntersville before it was flooded.

[4] Making several winds to the southeast, NY 129 connects to the Gate House Bridge, soon running eastward through Yorktown.

[3] What is now NY 129 was developed in the early 20th century as part of a general project to improve access and transportation across the reservoirs.

[15] In fall 1988, the original Hunter Brook Bridge (less than 19 feet (5.8 m) wide) was replaced, as it was never designed to take heavy traffic such as concrete-mixing trucks.