It runs from the Uhlerstown-Frenchtown Bridge at the Delaware River border with Pennsylvania in Frenchtown east to an intersection with U. S. Route 202 and Route 31 at the Flemington Circle in Flemington.

Route 12 begins at the Uhlerstown-Frenchtown Bridge over the Delaware River in Frenchtown at the Pennsylvania / New Jersey border, where it connects to Pennsylvania Route 32.

The first bridge across the Delaware at Frenchtown was a six-span covered wooden bridge built in 1841 on the five piers that still stand today, and the community became a gateway to Pennsylvania.

The Uhlerstown-Frenchtown Bridge, a free Delaware River Joint Toll Bridge Commission bridge over the Delaware River connects Frenchtown to Uhlerstown, Bucks County, Pennsylvania.

Frenchtown also borders the Commonwealth of Pennsylvania and is south of Milford borough.

Treasure Island is a Boy Scout property located between Point Pleasant, Pennsylvania and Frenchtown, New Jersey, United States.

On March 28, 1877, the New Castle and Frenchtown was merged into the Philadelphia, Wilmington and Baltimore Railroad, part of the Pennsylvania Railroad system.