When the Trenton Freeway was completed north to US 1, the US 1 designation was shifted to the freeway, replacing Route 174. U.S. Route 1 crosses the Delaware River into New Jersey on the Trenton–Morrisville Toll Bridge, which is maintained by the Delaware River Joint Toll Bridge Commission. Once in Trenton, US 1 becomes the Trenton Freeway and is maintained by the New Jersey Department of Transportation. US 1 meets Route 29 at a partial diamond interchange just north of the river. As the road heads through the downtown area with Amtrak’s Northeast Corridor running next to the route on the east side, it has a southbound exit and entrance with Warren Street that provides access to the New Jersey State House. It then comes to an interchange with the northern terminus of Route 129 as well as the western terminus of Route 33 near the Trenton Transit Center serving Amtrak, NJ Transit's Northeast Corridor Line and River Line, and SEPTA's Trenton Line. At this point, the Trenton Freeway turns onto a depressed alignment, with Conrail Shared Assets Operations' Enterprise Industrial Track closely parallel to the east, and comes to an interchange with Perry Street. The route turns northeast directly over the Delaware and Raritan Canal, which still flows underneath, and has an exit for Olden Avenue. The freeway has a northbound ramp for Mulberry Street before the parallel railroad tracks curve east away from the road and there is a northbound exit and southbound entrance from the median that provides access to US 1 Business and US 206. Past this interchange, US 1 continues into Lawrence Township, where the surroundings become more wooded as the freeway has an exit for Whitehead Road. Along this stretch, the freeway closely parallels the canal, which emerges from under the freeway just north of Mulberry Street. The Trenton Freeway ends at the point US 1 Business merges back into US 1. Here, US 1 becomes a four-lane divided surface road with jughandles called the Herbert Highway that is lined with suburban businesses. Continuing northeast, the first intersection along this road is with the eastern terminus of CR 546 (Franklin Corner Road). After this intersection, the road crosses the Delaware & Raritan Canal again prior to a modified cloverleaf interchange with I-295. Past this point, US 1 widens to six lanes as it has an interchange providing access to the Quaker Bridge Mall to the east of the route. A short distance later, there is a cloverleaf interchange with CR 533 (Quakerbridge Road).