 New York State Route 9D | ||||
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 Map of the Hudson Valley with NY 9D highlighted in red | ||||
| Route information | ||||
| Auxiliary route of US 9 | ||||
| Maintained by NYSDOT and the city of Beacon | ||||
| Length | 25.21 mi[1] (40.57 km) | |||
| Existed | 1935[2]–present | |||
| Major junctions | ||||
| South end |   US 6 / US 202 in Cortlandt | |||
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| North end |   US 9 / CR 77 in Wappingers Falls | |||
| Location | ||||
| Country | United States | |||
| State | New York | |||
| Counties | Westchester, Putnam, Dutchess | |||
| Highway system | ||||
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New York State Route 9D (NY 9D) is a north–south state highway in the Hudson Valley region of New York in the United States. It starts at the eastern end of the Bear Mountain Bridge at an intersection with U.S. Route 6 (US 6) and US 202 in Westchester County, and follows the eastern shore of the Hudson River for 25.21 miles (40.57 km) to a junction with US 9 north of the village of Wappingers Falls in Dutchess County. While US 9 follows a more inland routing between the bridge and Wappingers Falls, the riverside course of NY 9D takes the route through the village of Cold Spring and the city of Beacon.
The route was acquired by the state of New York in pieces over the course of the early 20th century. The part north of Beacon was entirely state-maintained by the end of the 1910s, while delays in rebuilding the remainder of the highway to state highway standards kept New York from fully acquiring the road until the early 1930s. NY 9D was assigned as part of the 1930 renumbering of state highways in New York, extending only from Beacon to Wappingers Falls. It was extended south to the Bear Mountain Bridge by the following year.