Nassau County Route 15 is a 4.02-mile (6.47 km), unsigned county road in Nassau County, on Long Island, New York. It travels between Port Washington Boulevard in Port Washington at its northern end and Old Northern Boulevard in the Village of Roslyn at its southern end. A small portion also passes through the Village of Flower Hill.

New York State Route 101 (NY 101) is a 3.58-mile (5.76 km) long state highway in northwestern Nassau County, New York, in the United States. It runs north–south as Port Washington Boulevard from NY 25A in Flower Hill, west of Roslyn and east of Manhasset, to Astor Lane in Sands Point. It becomes County Route 101 (CR 101) south along Searingtown Road to Shelter Rock Road (CR 8) and becomes Middle Neck Road north of Astor Lane, continuing north and west to a dead end at the Long Island Sound as the unsigned County Route D55 (CR D55).