The outlet lock at this location was built to allow canal boats to pass between the Delaware & Raritan Canal and Pennsylvania's Delaware Canal. Canal boats loaded with coal from the Lehigh Valley would come down the Lehigh Canal to Easton, Pennsylvania, where they would transfer to the Delaware Canal. They would then navigate the Delaware Canal to New Hope, cross the Delaware River after being attached to a cable that was strung across the river, and enter the D&R Canal through this lock. From here, most of the boats passed through Trenton before going on to New Brunswick and then into New York Harbor.
This structure was built in 1848, fourteen years after the D&R Canal was opened, and was abandoned in 1912. During the peak years of operation for canals in Eastern United States, the two decades following the Civil War, this cable system was in constant use from the earliest morning until nightfall. In 1868 the Lambertville Beacon reported an average of 31 boats per day crossed the Delaware River via this cable. The mules were led up to the New Hope/Lambertville Bridge, crossed the river and then came clomping through town to be re-connected to the boats.
Boats were connected to the cable at an angle to the current (with the bow end of the boat upstream of the stern) so that the force of the current would propel the boat across
the river. The angle was changed in relation to the force of the current.
The Belvidere-Delaware Railroad crossed the outlet lock on a fixed bridge that was high enough for boats to pass under.
The dam across the Delaware River downstream of this crossing was built to provide power to the Union Paper Mill in New Hope, to supply water to the lower half of the Delaware Canal and to make a pool in the Delaware River to facilitate the canal boat crossing.
The widening of the D&R Canal at this location was created to allow boats the room to make the 90 degree turn into the Outlet Lock and to provide room for boats to wait their turn for the crossing.