- Western Terminus:
- I-78 and US 22 in Stewartsville
- Eastern Terminus:
- Beaver Avenue (Hunterdon CR 626) in Clinton
- 14.62 miles
- Warren, Hunterdon
NJ 173 is an east/west route running next to I-78/US 22 from Stewartsville to Clinton. It follows the old alignment of US 22 in the area where it is now routed along I-78. The entire length is a two-lane undivided road, mostly through rural surroundings.