Past the freeway portion, the route heads northwest along the border of Morris and Passaic counties as a four- to six-lane arterial road with a wide median at places, winding through mountainous areas and crossing the interchange with I-287 in Riverdale.

The route continues northwest through Sussex County as a mostly two-lane surface road that passes through farmland and woodland as well as the communities of Franklin, Hamburg, and Sussex before reaching the New York state line, just south of an interchange with I-84 and US 6 in Port Jervis, in Montague Township near High Point State Park.

Following this, the roadway passes west of the Mother's Park & Ride, a park and ride facility serving NJ Transit buses, and reaches an interchange with CR 683, where the Newark–Pompton Turnpike leaves Route 23 and US 202, which continue north from this point as a surface road through commercial areas.

The route runs through Kinnelon, passing over the NYSW New Jersey Subdivision line, before entering Butler.

In Butler, Route 23 passes through commercial areas, crossing the intersection with Boonton Avenue (CR 511) before heading northwest.

Upon leaving Kinnelon, the route enters West Milford in Passaic County at the crossing of the Pequannock River.

[1] At this point, the route enters a more wooded, mountainous setting, following the Pequannock River and the NYSW line.

The southbound lanes cross the Pequannock River into Jefferson Township, Morris County, and CR 513 splits from Route 23 by heading south on Green Pond Road.

The road heads to the northwest through wooded mountains and runs through the community of Stockholm, where it passes east of a park and ride lot located at a church.

The route curves west onto a winding road, passing over the New York, Susquehanna, and Western Railway]] line.

The roadway gains a wide painted median, crossing into Franklin and meeting the intersection with Munsonhurst Road (CR 517).

The route crosses back into Hardyston Township, heading north through a mix of farms and forests.

[1][2] Route 23 crosses the Wallkill River into Wantage Township and continues north to an intersection with Glenwood Road (CR 565), running concurrently with that route and gaining a wide painted median past that intersection which eventually turns into a center left-turn lane.

[2] The route descends through Montague Township along a winding road, passing by some businesses immediately before heading to the New York state line.

A few feet after the state line, CR 15 comes to an interchange with I-84 before it ends at an intersection with US 6 in Port Jervis.

[18] This proposed freeway, which was to cost $120 million, was cancelled in the early 1970s due to financial troubles and feared environmental issues.

[19] A 1966 proposal called for Route 23 to be extended south as a freeway to I-287 in Piscataway in Middlesex County, running parallel to the Garden State Parkway.

With this project, the bridge over the Papakating Creek was replaced and a new road for the southbound lanes was built as an extension of Walling Avenue, while the original Route 23 became northbound only.