Davis Island Lock & Dam
Avalon, Allegheny County, Pennsylvania
Marker Inscription
Below this bridge was the first lock and dam built (1878-1885) on the Ohio River. This was the world's largest movable dam yet constructed, and included the world's first rolling lock gate and widest lock chamber. Built and operated by the U.S. Army Corps of Engineers; replaced by the nearby Emsworth Locks and Dams in 1922.
Erected by Pennsylvania Historical and Museum Commission
The Story
In the decades after the Civil War, the U.S. Army Corps of Engineers set out to tame the Ohio River for year-round navigation. Their first lock and dam on the river, built here between 1878 and 1885, was a marvel of its day—the largest movable dam yet constructed, with the world's first rolling lock gate and its widest lock chamber. It served until 1922, when the nearby Emsworth Locks and Dams replaced it.
Why it matters
Davis Island proved that America's great inland rivers could be engineered into reliable commercial highways, opening the pattern of locks and dams that made the Ohio a backbone of national commerce.
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