Which Ohio river's 1969 fire is cited as helping build momentum for Earth Day?

The Ohio river whose 1969 fire is cited as helping build momentum for Earth Day was the Cuyahoga River.

On June 22, 1969, an oil slick on the heavily industrialized river caught fire after a spark from a passing rail car. The blaze was brief and caused about $50,000 in damage, much of it to a railroad bridge, but it became a powerful symbol of unchecked pollution.

The Cuyahoga had caught fire many times before, including a much larger 1952 blaze. The 1969 incident gained wider attention after national coverage highlighted the river’s extreme pollution. It helped energize support for stronger environmental protections, alongside events such as the Santa Barbara oil spill.

The fire did not single-handedly create Earth Day, which was organized through several environmental campaigns. But it became one of the era’s most memorable examples of why public action was needed. Later reforms included expansion of federal water-pollution controls and the creation of the Environmental Protection Agency.