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The Chicago River | © Daniel X. O'Neil / Flickr
The Chicago River | © Daniel X. O'Neil / Flickr

How the Chicago River Was Reversed

Picture of Tim Marklew
Updated: 18 May 2017

Today, the beautiful waters of Lake Michigan and the Chicago River are among the city’s biggest attractions, but Chicago hasn’t always treated them well, a problem that once necessitated a huge and incredible piece of engineering.

Unsurprisingly, given its location, the city’s main supply of water has always been Lake Michigan. However, in the second half of the 19th century, as the city began to boom with industrialization, the river was frequently mistreated and polluted with waste and sewage, all of which would then drain into the lake. The drinking water for the city soon became polluted, leading to serious outbreaks of typhoid and other waterborne diseases for residents. It’s become an urban myth that a storm in 1885 exacerbated the problem and led to an epidemic that killed 12% of Chicagoans at the time. While no such singular disaster took place, in 1889, the Sanitary District of Chicago was formed to deal with city’s sanitation problems.

The idea to reverse the flow of the river away from the lake had already been unintentionally attempted in 1871, when the existing Illinois and Michigan canal was deepened, unexpectedly pulling in water from the Chicago River. Although the effects were only temporary, a solution had been found. In order to achieve a permanent reversal, the city began construction on a new canal to join the Chicago River with the Des Plaines River, which would also benefit the city by providing a continuous transportation link from the Great Lakes to the Gulf of Mexico.

While the idea was relatively simple, using gravity to make water flow from the river into the continually deepening canal and then into another river, the construction was not. Beginning in 1892, the “Main Channel” first phase of the Chicago Sanitary and Ship Canal took eight years to complete, as nearly 40 million cubic yards of earth and rock were removed all along the 28-mile (45-kilometer) stretch. The project required new innovative techniques, establishing what some called the “Chicago school of earth moving,” also used in the construction of the Panama Canal. In 1900, when the first phase of the canal opened, the river was permanently reversed and the waste problem solved.

Although the system would eventually be named a “Civil Engineering Monument of the Millennium” by the American Society of Civil Engineers (ASCE), not everyone was happy at the time. Missouri objected, fearing that all of Chicago’s pollution would flow down the Des Plaines River, into the Illinois River and finally into the Mississippi, which was the source of St. Louis’s drinking water. In 1906, the state of Missouri sued Illinois, but the U.S. Supreme Court ruled in favor of Illinois, stating that there was no evidence that the water quality in the Mississippi had been affected.

Construction continued uninterrupted, and the canal was extended several times, including the building of other canals to support and perfect the system. With the reversal of the river, the water supply greatly improved, along with Chicagoans’ health. A truly groundbreaking achievement in more ways than one.