Route 20 begins at an interchange with U.S. Route 46 and County Route 630 (Crooks Avenue) just north of the Garden State Parkway on the border of Clifton and Paterson. The road follows the bend of the Passaic River directly north of Dundee Lake, heading to the north into Paterson as McLean Boulevard, a four-lane divided highway. The route runs in between the Passaic River to the east and two large cemeteries to the west before coming to an interchange with Interstate 80 and Market Street. Past Interstate 80, Route 20 becomes a six-lane divided highway that heads under New York, Susquehanna and Western Railway's New Jersey Subdivision line and through a mix of residential and commercial areas.