The southern segment begins in Downtown Dover at an intersection with US 46 and Mount Hope Avenue (CR 661).

[2][3] From the new intersection with US 46, Route 15 continues north on West Clinton Street, exiting Dover and entering Rockaway Township.

A mile north, the road becomes a four lane divided highway with exits for a few businesses and Picatinny Arsenal.

In Jefferson Township, the northbound and southbound lanes become about a quarter mile apart as it climbs up a steep mountain.

It continues into Frankford Township and comes to an end at the intersection of U.S. Route 206 and Sussex Road (CR 565).

[6] In 1804, this road was legislated as a part of the Union Turnpike, which ran from Morristown north[citation needed].

[citation needed] In 2004, State Department of Transportation Commissioner Jack Lettire and state Senator Robert Littell announced the completion of a project of restructuring the Route 15-Houses Corner Road intersection, which broke ground in 2002 at the hand of then-governor James E. McGreevey.

[7] Wilson Drive and White Lake Road were also realigned to form one signalized intersection, with completion originally expected in 2008.

The project cost the state $2.3 million (2009 USD) to fund for construction by the North Jersey Transportation Planning Authority.

[12] There is an ongoing local grassroots movement[dubious – discuss] to honor the late U.S. President Ronald Reagan by renaming Route 15 after him.

Most recently on February 2, 2012, a bill was introduced in the New Jersey General Assembly by Assemblymen Michael Patrick Carroll, Gary R. Chiusano, Jay Webber and Assemblywoman Alison Littell McHose to designate Route 15 as the "Ronald Reagan Memorial Highway".