- Southern Terminus:
- Paterson Plank Road (NJ 120) in Carlstadt
- Northern Terminus:
- South Pearl Street (NY 304) at the New York-New Jersey state line
- 17.95 miles
CR 503 is a north/south route in the northern section of New Jersey. It begins at the northern end of the freeway section of NJ 120 and runs north along Washington Avenue, Moonachie Road, and Liberty Street to Hackensack, where Moonachie Road curves to the east and ends at South River Street. CR 503 turns back to the north along South River Street, which after a short distance changes names to become River Street and then Hackensack Avenue. There is an interchange with the NJ 4 freeway on Hackensack Avenue. Just north of this interchange, CR 503 turns west onto Main Street for a couple of blocks and then north onto Kinderkamack Road. It follows Kinderkamack Road north until the New York-New Jersey state line, where it becomes South Pearl Street (NY 304).
Kinderkamack Road is a two-lane undivided road. Most of the other portions of CR 503 have four lanes, and some sections are divided.