It travels between Port Washington Boulevard (NY 101) in Port Washington at its northern end and Old Northern Boulevard (CR D71 / CR 7A) in the Village of Roslyn at its southern end.

[3][7] Starting at its northern end, County Route 15 begins in Port Washington, at the intersection of Beacon Hill Road, Main Street, and Port Washington Boulevard (NY 101).

[6][9] From there, CR 15 continues south through Flower Hill, passes underneath the William Cullen Bryant Viaduct (NY 25A), and then enters the Village of Roslyn immediately thereafter.

[3][8][9] County Route 15 is classified as a minor arterial highway by the New York State Department of Transportation and is eligible for federal aid.

[3][8][9][1] The CR 15 designation for West Shore and Beacon Hill Roads can be traced back to 1959, when the Nassau County Department of Public Works created a numbered highway system as part of their "Master Plan" for the county highway system.