- Southern Terminus:
- Woodbury Road (Nassau CR 12/Suffolk CR 11) in Cold Spring Harbor
- Northern Terminus:
- NY 25A in Cold Spring Harbor
- 1.72 miles
Just east of the Nassau-Suffolk county line, Northern Boulevard ends and NY 25A is routed north along a street called Harbor Road. The section of Harbor Road south of this intersection is designated NY 108. It is a two-lane undivided road that runs parallel to the Nassau-Suffolk county line. It has its southern terminus at Woodbury Road (Nassau CR 12/Suffolk CR 11) by the Cold Spring Harbor train station.