- Western Terminus:
- Union Avenue (CR 63) in Westbury
- Eastern Terminus:
- Harbor Road (NY 108) and Woodbury Road (Suffolk CR 11) at the Nassau-Suffolk county line
- 8.81 miles
CR 12 runs through the eastern portion of Nassau County from Westbury to the Nassau-Suffolk county line. It begins at Union Avenue (CR 63) and is called Prospect Avenue. It runs east to Cantiague Road, where it changes names to become West John Street, which continues east through Hicksville. West John Street ends at Broadway (NY 107), slightly south of the southern end of the NY 106/NY 107 multiplex. CR 12 is multiplexed with NY 107 for one block and then splits off onto East Barclay Street, which runs east for a short distance before changing names to become Woodbury Road. Woodbury Road runs diagonally to the northeast until it reaches the Nassau-Suffolk county line at the southern terminus of Harbor Road (NY 108). Woodbury Road continues into Suffolk County as Suffolk CR 11. CR 12 is a two- to four-lane road and is undivided in most places. It crosses the Wantagh Parkway, the Long Island Expressway (I-495), the Northern Parkway, and the Seaford-Oyster Bay Expressway (NY 135), but it does not have interchanges with any of these highways. Motorists may access Woodbury Road from the Long Island Expressway or the Northern Parkway by using either Manetto Hill Road or Sunnyside Boulevard.