Outlet Lock at Lambertville, c.1900

When the D&R Canal first opened for operation in 1834, there were 14 lift locks along the 44-mile main stem of this transportation waterway between Bordentown and New Brunswick. Along its 22-mile feeder, which flowed south from Bulls Island to Trenton, there was only one lift lock and one outlet lock; both were located at Lambertville.

Whenever an elevation change occurs in the topography along the route of a canal a lift lock is needed to overcome it. Think of them as a water-filled elevator that lifts or lowers a vessel from one level along the corridor to the next. Locks are needed to maintain an even, controlled flow of water on this “highway” for boat traffic. Few locks were needed on the D&R Canal. This contour canal was surveyed to follow a relatively level stretch of land along the narrowest central section of the state between the Delaware and Raritan rivers. The highest elevation along the route was 56 feet above sea level at Trenton.

East Millstone A-Frame Swingbridge

The locks visitors see today along the D&R are altered-- missing are the doors that “locked” boats in. Today water enters the lock through a sluice gate on the upstream end. When the canal was in operation, this was the location of the drop gate; a heavy wood door that pivoted at the bottom and when opened, lay horizontal and flat under the water allowing boats to float over it. At the downstream end were two large wood mitre gate doors that pivoted vertically (like French doors). When in the closed position the mitre gates rested at angle against the upstream flow of water, creating a tight seal. 

Both the drop and mitre gates had smaller doors built into them. These smaller doors were called wicket gates and they allowed water to enter or exit the lock. There were eight wicket gates cut into each mitre door, located under water level. The lock tender would operate each wicket gate independently using a “lock key”, a wrench-like tool which opened the gates allowing water to exit the lock and lower the boat to the downstream level. In contrast, the upstream wicket paddles laid flat on the floor of the drop gate and allowed water to rush into the lock chamber and raise the boat.

The lock tender assigned at all the locks along the canal lived in houses built and owned by the Canal Company. All the canal company lock houses were constructed in 1833-34 and were provided to the tender assigned at each lock location as part of his salary.

Drop Gate Wicket Paddles

By the 1850s, the length of all the locks on the D&R Canal were doubled to 220 feet to accommodate the increasing boat traffic. The original upstream mitre gates were replaced with the drop gates expediting the locking process. The longer lock allowed for two 90-100 feet boats to be locked through at the same time. With the new drop gate at the upstream end, the entire process, from entering to exiting the lock, took about 15 minutes. 

With the closing of the canal in 1932, the wood covered masonry locks sat unused. By 1936 the defunct D&R Canal became the property of the State of New Jersey and its fate was uncertain. However after heated debate, a new use for the old canal as a state water supply was approved. The transformation began in the late 1940s as the drop gates, mitre doors, and mechanisms were removed, replaced by the modern sluice gates. Today only the shell of the masonry lock, now covered in concrete, is left as a reminder of the part it played in the D&R Canal story.