Currently owned and maintained by the Nassau County Department of Public Works for most of its length as the unsigned Nassau County Route 189, the road was formerly owned and maintained by the New York State Department of Public Works (and later by NYSDOT) as New York State Route 115 from c. 1932 until July 1, 1972.

It then heads north for 0.48 miles (0.77 km), continuing straight for three blocks, passing St. Regis Street before reaching a dead-end next to the Wantagh State Parkway.

[2][3] Immediately on the other side of the Wantagh State Parkway, Wantagh Avenue resumes at a signalized intersection with Merrick Road (CR 27); this location marks the start of Nassau County's ownership and the CR 189 designation – and the southern end of the main, 5.25-mile (8.45 km) segment of the road.

[2][3][4] From there, it heads north, soon intersecting Sunrise Highway (NY 27) and passing underneath the Wantagh station on the Long Island Rail Road's Babylon Branch immediately thereafter.

It then continues north-northeast through North Wantagh and shortly thereafter reaches a cloverleaf interchange with the Southern State Parkway; Wantagh Avenue crosses over the parkway and immediately thereafter reaches an intersection with North Jerusalem Road (CR 181) adjacent to MacArthur High School, entering Levittown and veering northeast.