In the late 19th century, Chicago faced a public health nightmare. The rapidly growing metropolis dumped its industrial waste and raw sewage directly into the Chicago River, which naturally flowed east straight into Lake Michigan—the city's primary source of fresh drinking water. Waterborne diseases like cholera and typhoid fever swept through the population, forcing civic leaders to take drastic action.
The solution was the Chicago Sanitary and Ship Canal project, an astounding civil engineering endeavor aimed at literally reversing the flow of the Chicago River away from the lake and toward the Mississippi River watershed. Led by Chief Engineer Isham Randolph, workers spent eight years excavating over 40 million cubic yards of earth and rock, using steam shovels and dynamite to cut a 28-mile channel deeper than the river bed itself. By constructing a series of massive canals and controlled lock systems, engineers altered the regional topography so gravity would pull water from Lake Michigan westward into the Des Plaines River instead.
On January 2, 1900, fearing a legal injunction from Missouri, engineers secretly blasted open the final rock dam before courts could intervene. The operation succeeded seamlessly, redirecting the flow of sewage away from Lake Michigan and drastically improving public health, though it sparked decades of legal disputes over water rights and environmental impacts downriver.