An illustration of the incline plane. NPS image
By Elliot Carter
A water-filled boat elevator used to lower barges from the C&O Canal down to the Potomac River. Technically referred to as the "Incline Plane," this engineering oddity allowed canal traffic to bypass the gridlock in Georgetown and quickly travel to other parts of the canal system.
The innovative boat elevator was designed by the Potomac Lock and Dock Company in 1875 and was instantly recognized as a marvel of the industrial revolution. It was one of just two projects that were selected as the best representations of American engineering at the 1878 Paris Exposition (the other project was the Brooklyn Bridge).
Photo of the incline plain in operation. C&O Canal National Historical Park photo
The system was very simple conceptually. A bathtub-like "caisson" was dragged up railroad tracks to the canal, the boat sailed in, and the rig went back down. Karen Gray of the Washington Canal Association describes the procedure in greater detail:
"The incline worked by bringing the caisson up against a gated headwall in the towpath berm of the canal, to which the caisson would be held fast. The headwall and caisson gates were then opened, admitting water into the caisson and, once it was filled, a boat. When ready to descend, the gates would be closed and the caisson would descend down the incline to a river basin where the caisson’s lower gate was opened, allowing the boat to pass into the basin where it would be connected to a tug for its journey downriver. The entire process took only 12 to 18 minutes."
The caisson's descent was controlled by two heavy counterweights, just like a modern elevator. When it came time to bring the counterweights back to the top, they were pulled by turbines that generated power from the canal water (later upgraded with steam power).
Why Build It?
The boat elevator was an expensive bid to increase efficiency on the C&O Canal system. Canal Company President James C. Clark described how “a string of loaded boats from half mile to a mile in length is seen lying above the Collector’s Office in Georgetown, waiting their turn to get in to the wharves to discharge their cargoes.” Located a few miles up from Georgetown, the boat elevator gave captains an option to bypass the gridlock if they were headed for a different destination.
NPS notes that when it was built in 1875, the Canal Company was "riding a wave of prosperity, [as] more than 500 boats had plied the canal [that year]. This prosperity was just a blip. Even with the Boat Elevator, canals in in the United States saw huge losses against the growing railroad companies in the late 19th Century.
The Boat Elevator ended up getting destroyed by a flood in 1889 that also damaged miles of the C&O towpath. Collectively, these losses forced the Canal Company into bankruptcy.
Today all that is left is a stone platform on the towpath and a plaque. You can visit, it's 2 miles up the towpath from Georgetown.
The remains of the incline plane. Elliot Carter photo
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