Chicago River

One might think the U.S. stopped dumping raw sewage into its rivers after the passage of the Clean Water Act outlawed it in 1972. Yet in many cities old sewers that overflow with rainwater, crumbling century-old pipes and, in the case of Chicago, sewers that discharge directly into its namesake river, continue to this day. According to American Rivers, the Chicago is "one of the only rivers in the country where undisinfected sewage is dumped directly into the river every day" and the problem could be solved if the Illinois Pollution Control Board required disinfection of the city's wastewater. The thing is, wastewater treatment is not cheap, estimated to cost in the hundreds of millions of dollars.