Niagara Falls has seen plenty of dramatic stunts over the centuries, ever since a local hotel owner sent a condemned ship with a “cargo of ferocious animals” over the falls in 1827. (Only the goose survived the plunge.) But no feat has attracted more visitors than a scientific survey conducted in 1969. That year, the U.S. Army Corps of Engineers turned off American Falls. The engineers wanted to find a way to remove the unseemly boulders that had piled up at its base since 1931, cutting the height of the falls in half. But the study itself proved more appealing than any improvement they could recommend. The first weekend after the “dewatering,” about 100,000 people showed up to see this natural wonder without its liquid veil.

The performance will have an encore at some point in the coming years when New York State once again dewaters American Falls. The purpose this time is more pedestrian—to replace two bridges—but the process will be the same. Engineers will construct a dam between the American bank of the Niagara River and the eastern tip of Goat Island, stopping the flow of water—nearly 76,000 gallons every second—over the 11-story drop.

Will crowds show up this time? Photos from 1969 suggest the bedrock is nothing special to behold. Without water, American Falls is merely a cliff. And yet the spectacle fulfills a fantasy older than the American nation: human mastery over nature. To sap the falls completely would seem to be the ultimate triumph—but, in fact, Niagara Falls was long ago brought to heel.

The falls—American Falls, Horseshoe Falls and the small Bridal Veil Falls—formed some 12,000 years ago, when water from Lake Erie carved a channel to Lake Ontario. The name Niagara came from “Onguiaahra,” as the area was known in the language of the Iroquois people who settled there originally. After the French explorer Samuel de Champlain described the falls in 1604, word of the magnificent sight spread through Europe.

A visit to Niagara Falls was practically a religious experience. “When I felt how near to my Creator I was standing,” Charles Dickens wrote in 1842, “the first effect, and the enduring one—instant lasting—of the tremendous spectacle, was Peace.” Alexis de Tocqueville described a “profound and terrifying obscurity” on his visit in 1831, but he also recognized that the falls were not as invincible as they seemed. “Hasten,” Tocqueville urged a friend in a letter, or “your Niagara will have been spoiled for you.”

To many, these cataracts were not natural wonders but natural resources. When Tocqueville visited, factories already encroached on the water’s edge. In 1894, King C. Gillette, the future razor magnate, predicted Niagara Falls could become part of a city called Metropolis with 60 million people. A few years later, Nikola Tesla designed one of the first hydroelectric plants near the falls. He saw it as a high point in human history: “It signifies the subjugation of natural forces to the service of man.”

Niagara Falls today is the result of the push and pull of exploitation and preservation. The Free Niagara Movement successfully lobbied to create a park around the site in the 1880s, but the changes continued. In 1950, the United States and Canada decided to divert 50 percent of the water from Niagara Falls through underwater tunnels to hydroelectric turbines during peak tourist hours. At night, the water flow over the falls is cut in half again. (Engineers manipulate the flow using 18 gates upstream.)

The historian Daniel Macfarlane has called the modern falls “a completely man-made and artificial cataract.” Ironically, this has maintained them as a tourist attraction. People want to see the image they recognize from postcards, but the Niagara Falls, left to its own devices, is one of the fastest-eroding falls in the world. It has moved seven miles since it formed; the diversion of water has helped reduce the rate of erosion by more than 85 percent.

The engineers who built the diversion tunnels also made several modifications to the actual falls. They excavated both edges of Horseshoe Falls to create a visually pleasing crest. The 1969 dewatering was another aesthetic intervention, but the engineers decided, surprisingly, to leave the fallen boulders alone. “Recent emphasis on environmental values has raised questions about changing natural conditions even for demonstrated natural and measurable social benefits,” they wrote in their final report.

At some point, the United States and Canada will face the same dilemma again: Do they intervene to maintain the falls or let natural processes unfold? Even with the decreased rate of deterioration, the falls regress a little every year. In about 15,000 years, the cliff edge will reach a riverbed of soft shale—and then Nature will upstage any human efforts. Niagara Falls will crumble and irrevocably disappear.

Cataract Surgery

One June day 50 years ago, engineers tackled a seemingly impossible feat—
turning off American Falls

Research by Keith Rutowski

Ben Crair | READ MORE

Ben Crair writes frequently for the New Yorker, New York magazine and Bloomberg Businessweek.