Here, the route crosses the Appalachian Trail and runs adjacent to part of Hudson Highlands State Park, a preserve covering three non-contiguous areas between Peekskill and Beacon.

[3] From the county line to the hamlet of Garrison, a distance of 4 miles (6.4 km), NY 9D passes a few historical areas, such as the house Benedict Arnold was holed up in prior to his treason, the point of land where he caught the ship downriver to New York City, and the eastern end of the chain that was strung across the Hudson River during the American Revolution to prevent ships from coming upriver north of West Point.

[3] From Garrison, NY 9D heads through a 5-mile (8 km) stretch of lightly developed areas, intersecting County Route 11 (CR 11, named Snake Hill Road), another connector to US 9, and passing the Boscobel mansion on its way into the village of Cold Spring.

Past the village line, the route parallels the Metro-North Railroad for 2 miles (3 km) through another portion of Hudson Highlands State Park.

The road soon reaches the southern edge of the city of Beacon, where it becomes Wolcott Avenue and the surroundings transition from rural mountainous scenery to an urban setting.

The highway crosses Fishkill Creek ahead of another 90-degree turn, this time to the northeast, giving NY 9D an S-shaped alignment as it travels through downtown Beacon.

The highway runs by several housing tracts and Dutchess Stadium, the home of the Hudson Valley Renegades, a Single-A Minor League Baseball team, before crossing into the adjacent town of Wappinger.

[3] Across the town line, the road takes on a straighter northeasterly track that brings it east of the hamlets of Chelsea and New Hamburg, both of which lie roughly 1 mile (1.6 km) to the west on the banks of the Hudson.

NY 9D traverses several blocks of homes on the eastern edge of the Wappingers Falls Historic District before it meets East Main Street at a T-intersection in the center of the village.

Past the creek, the route changes names to West Main Street and makes a sharp bend to the north, passing the Bain Commercial Building and running alongside Wappinger Lake for a short distance before leaving the village limits.

The road serves a handful of homes on the northern fringe of Wappinger Falls prior to entering a commercial district surrounding a junction with US 9 near the South Hills Mall and the Poughkeepsie Galleria.

[15] Construction on parts of the road was stalled for years, however, with the delay on the stretch north of Cold Spring being attributed to problems in acquiring the highway's right-of-way.