- Southern Terminus:
- Merrick Road (CR 27) in Merrick
- Northern Terminus:
- Wheatley Road in Old Westbury
- 9.84 miles
Merrick Avenue is a major north/south route in southern central Nassau. It becomes a county route at Merrick Road (CR 27) in Merrick and runs north, parallel to the Meadowbrook Parkway. North of Hempstead Turnpike (NY 24), it is the western boundary of Eisenhower Park. It ends at Old Country Road (CR 25), north of which it becomes Post Avenue. The southern section of Merrick Avenue has two lanes and the northern section has four lanes. Most of it is undivided.
Post Avenue runs north from Old Country Road (CR 25) through Westbury to Jericho Turnpike (NY 25). The entire length is a two-lane undivided road. At Jericho Turnpike (NY 25), Post Avenue changes names to become Post Road, which runs north through Old Westbury and is also a two-lane undivided road. Post Road ends at Wheatley Road in Old Westbury.