Rivers in industrial cities, laden with raw sewage and oil-soaked debris, used to catch fire a lot in the early part of the 20th century, and nobody would give them much mind. But when the Cuyahoga River caught fire in 1969, attitudes had changed, and "the Mistake by the Lake" sparked environmental reforms across the country. Within a year, the Environmental Protection Agency would be established and the first Earth Day would be held. Today, 40 years later, Cleveland is celebrating the Cuyahoga's rebirth, now home to more than 60 species of fish as well as beavers, blue herons and bald eagles. Click here to read on.