The route remains similar in design for several miles, crossing into the town of New Castle as a two-lane residential road.

The two routes wind eastward along a two-lane residential road, passing Gedney Park and leaving the hamlet of Millwood.

[3] NY 133 continues northeast on Millwood Road as a two-lane residential street, winding through the town of New Castle, passing numerous homes for a couple miles.

After making a turn to the east, NY 133 intersects with Seven Bridges Road (unsigned County Route 5 (CR 5)).

Just after crossing into Mount Kisco, NY 133 enters an interchange with exit 34 of the Saw Mill River Parkway.

Here the name changes to Main Street, and NY 133 passes the Mount Kisco Metro-North station.

[5] The Croton Turnpike Company was established on April 6, 1807 by charter from the New York State Assembly at the cost of 12.5 cents per wagon with at least two horses.

[6] By the middle of the 19th century, the Croton Turnpike had been dissolved,[5] after an 1849 request to repeal the charter given in 1807 had passed the Assembly.

Designated State Highway 143 (SH 143), the alignment was first contracted in 1903 for a 3.14 miles (5.05 km) segment of macadam.

The 1.89 miles (3.04 km) segment cost $28,313.22 (1915 USD), with the state giving in $18,402.94 in funds for the project.