Fires were nothing out of the ordinary on Cleveland’s Cuyahoga River in the 1960s. The city was still a manufacturing hub and the river, which empties into Lake Erie, had long been a dumping place for sewage and industrial waste.

But on June 22, 1969, a spark flared from the train tracks down to the river below, igniting industrial debris floating on the surface of the water. Flames spread across the river, in some places reaching five stories high.

And though it only took about 20 minutes to extinguish the blaze, the not-so-unusual river fire helped create an environmental revolution. Though it initially caught the attention of few Cleveland residents, the Cuyahoga River Fire stoked the rest of the nation’s awareness of the environmental and health threats of river pollution—and fueled a growing movement that culminated in the creation of the Environmental Protection Agency.

A 1967 photograph, showing old cars used as rip-rap along the banks of the Cuyahoga River to protect it from erosion, is held in front the foliage-filled landscape of the river in 2006. Joshua Gunter/The Plain Dealer/AP Photo

Cleveland had staked its claim as an industrial center in the 19th century, when the Civil War turned the then-small city into a manufacturing powerhouse. As factories and the local population grew, sewage and industrial remnants poured into the river. But, in line with the era’s lax attitudes toward the environment, nobody much cared.

Soon, the river was filthy. “Yellowish-black rings of oil circled on its surface like grease in soup,” recalled František Vlček, a Czech immigrant, of his first view of the river in the 1880s. “The water was yellowish, thick, full of clay, stinking of oil and sewage. Piles of rotting wood were heaped on either bank of the river, and it was all dirty and neglected….I was disappointed by this view of an American river.”

At the time, according to the Property and Environment Research Center, Cleveland sourced its drinking water from Lake Erie and used the river as a sewer. "So municipal authorities left the Cuyahoga River alone—allowing firms along its banks to discharge into it at will,” they write.

Firemen stand on a bridge over the Cuyahoga River to spray water on the tug Arizona, after an oil slick on the river caught fire in 1952.

The waste those firms did discharge turned the river muddy and filled it with oil, solvents and other industrial products. Between 1868 and 1952, it burned nine times. The 1952 fire racked up $1.5 million in damage. But by most, occasional fires and pollution were seen as the cost of industry—a price no one was willing to dispute.

When fire broke out on the river again in 1969, it seemed like business as usual. “Most Clevelanders seemed not to care a great deal,” write environmental historians David Stradling and Richard Stradling. “Far too many problems plagued the city for residents to get hung up on a little fire…The ’69 fire didn’t represent the culmination of an abusive relationship between a city and its environment. It was simply another sad chapter in the long story of a terribly polluted river.”

But attitudes toward the environment had changed since the last river fire. In the years before the fire, Rachel Carson published Silent Spring, which became a bestseller and opened the eyes of many Americans to the danger of DDT and other pesticides. Congress had begun passing laws to boost air quality and protect endangered species. And a growing counterculture had begun to embrace sustainability as people experimented with back-to-the-land subsistence farming and communal living.

Another factor was at play: an enormous oil spill in Santa Barbara, California that sent 3 million gallons of oil into the Pacific Ocean. Suddenly, people’s televisions and newspapers featured images of oil-slicked birds and dead dolphins. Outraged and shocked, citizens mobilized to clean up beaches and lobby oil companies not to pollute.

“Never in my long lifetime have I ever seen such an aroused populace at the grassroots level,” said Thomas Storke, a Santa Barbara news editor. “The oil pollution has done something I have never seen before in Santa Barbara—it has united citizens of all political persuasions in a truly nonpartisan cause.”

Three men in a motor boat take water samples of the Cuyahoga River where the shore is lined with semi-submerged automobile wreckage in 1968. Alfred Eisenstaedt/The LIFE Picture Collection/Getty Images

Those same citizens soon opened their copies of Time Magazine to see a story on the Cuyahoga fire, along with a photo of the 1952 fire. The conditions it described, which included a river that “oozes rather than flows,” caught readers’ attention. (As the National Parks Services notes, many bought that issue of Time because it featured an exposé on the Chappaquiddick scandal.)

READ: Ted Kennedy’s Chappaquiddick Incident: What Really Happened

Soon, cries for regulation of water pollution became a roar. A grand jury investigation of the causes of the fire followed, as did coalition efforts to clean up the Great Lakes. It even inspired plans for a national environmental “teach-in”—an event that would become the first Earth Day. In early 1970, President Richard Nixon called for sweeping environmental reform. He created a council on environmental reform which, shortly afterward, was consolidated into the Environmental Protection Agency. In 1972, Congress overrode Nixon's veto to pass the Clean Water Act, which created national water quality standards.

Though the Cuyahoga River fire did not directly lead to the formation of the EPA, it was an important landmark for a burgeoning environmental movement. Today, the river is no longer stagnant or filthy. Public and private efforts have diverted sewage and cleaned up its banks. According to the National Parks Service, the river still has unhealthy amounts of sewage in some areas. But in March 2019, the Ohio EPA announced that its fish are now safe to eat.

Whether or not the river ever overcomes the remainder of its environmental challenges, the memory of the 1969 fire will continue to mobilize those intent on protecting the natural world.