In the summer of 1969, one of the most recognizable waterfalls on Earth went silent. The American side of Niagara Falls - which had roared continuously for roughly 12,000 years - was turned off. Not by accident. On purpose.

Why Engineers Needed the Water Gone

By the 1960s, a massive pile of fallen rock called talus had accumulated at the base of the American Falls, effectively halving the waterfall's visible height. The International Joint Commission - a binational U.S.-Canada body overseeing shared waterways - wanted to know whether the talus could be removed to restore the falls to their full dramatic drop. To study the rock properly, the water had to go.

Building the Dam

Starting June 9, 1969, the Albert Elia Construction Company, directed by the U.S. Army Corps of Engineers, Buffalo District, put more than 1,200 trucks to work dumping 28,000 tons of rock across a 600-foot stretch of the Niagara River between the mainland and Goat Island. Three days later, on June 12, the American Falls stopped flowing - for the first time since the end of the last Ice Age, roughly 12,000 years earlier. The Canadian Horseshoe Falls kept running throughout.

What the Dry Riverbed Revealed

The exposed cliff drew 100,000 visitors in the first week alone. Tourists walked where the waterfall had thundered minutes before. Geologists drilled into the riverbed, mapping faults and measuring erosion rates. Workers found two unidentified bodies in the dry rock - along with millions of coins thrown in by hopeful visitors over decades. Engineers installed steel bolts and cables to stabilize fragile sections including Luna Island.

The Counterintuitive Discovery

After months of analysis, the geologists delivered a surprise verdict: the talus pile was likely holding up the waterfall face. The debris was acting as structural support. Remove it and the cliff above could catastrophically collapse. The International Joint Commission rejected removal - citing both the structural risk and the estimated $26 million cost. Instead, engineers quietly reinforced the rock with bolts and anchors, and left the talus exactly as they found it.

Turning It Back On

On November 25, 1969, in front of 2,650 spectators, the temporary cofferdam was dynamited. The Niagara River reclaimed its course. The American Falls roared back to life, looking almost exactly as they had before. Five months of engineering work had produced one recommendation: leave it alone.

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