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Chicago Sanitary and Ship Canal
The Chicago Sanitary and Ship Canal was built in 1900 to replace the small Illinois and Michigan Canal that connected the Great Lakes (lake Michigan) to the Mississippi River. Prior to the completion of this canal, Chicago's waste water was dumped into Lake Michigan - the source of water for the city.
The modern canal is 28 miles long, 202 feet wide, and 24 feet deep, allowing plenty of room for barge traffic as well as an outlet for the city's treated waste water.