The Death and Life of the Great Lakes by Dan Egan:
In the opening stanze of his 1916 ode to Chicago, poet Carl Sandburg playfully refers to his City of the Big Shoulders as Hog Butcher for the World and Player with Railroads. He might also have added Conveyor of Crap, because less than two decades earlier Chicago built what is essentially a continental-sized commode, turning Lake Michigan into the world’s largest toilet tank, and the Gulf of Mexico into its toilet bowl. It was a matter of life and death for a mushrooming city that sent its sewage into Lake Michigan, from which it also takes its drinking water.
In the 1890s, in order to protect that drinking water, engineers began work on the Chicago Sanitary and Ship Canal. The city’s motives for the canal are made clear in its name; when it opened in 1900, its primary job was to flush the city’s waste across the continental divide and into the Mississippi River basin. It also, conveniently, doubled as a massive expansion of the original barge canal linking Lake Michigan to the Gulf of Mexico.
The rail-straight, 25-foot-deep canal that is as wide as a football field does a most remarkable thing. It reverses the flow of Chicago’s namesake river, which was in its natural state a shallow, slow-flowing dribble feeding Lake Michigan. Its headwaters were just several miles west of downtown at the bog Marquette and Joliet first came across in the late 1600s. The Sanitary and Ship Canal, which is lower than Lake Michigan, connects to this river. This pulls the formerly lake-bound river’s flow backwards. Instead of the river feeding Lake Michigan, the lake now feeds the river. The river then flows into the canal, the canal flows through the continental divide and into the Des Plaines River, which flows into the Illinois River, which flows into the Gulf-bound Mississippi River.