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The Chicago Sanitary and Ship Canal

The sanitary conditions in Chicago were getting worse and the I&M Canal, being strictly a ship canal, did little to help. The population was expanding. From DuSable and his family in 1779, the population slowly grew to 100 in 1830. After that growth was rapid: 5,000 in 1840; 30,000 in 1850; reaching 1 million in 1890 and 1.6 million in 1900.

To understand the problems of populating the area, we must picture the topography; the slope of the land from the high point of the portage to the lake is practically dead flat. The high point at the original portage was only seventeen feet above the lake, even flatter than the land east of Oak Park. It was a swampy area, difficult to drain. All of the sewage in the area simply dumped into the Chicago River. Attempts to divert the sewage into the I & M Canal were less than successful. Pumps could handle the steadily increasing flow in normal weather but during heavy rains, the Chicago River would revert to its original flow41 carrying untreated sewage into Lake Michigan, from where the City took its water supply.

Front-page articles in contemporaneous newspapers note that on August 2, 1885, 6.2 inches of rain fell on the city. Whereas sewage was washed into Lake Michigan, strong northeast winds prevented the wastewater from reaching the city’s water intakes. There was no adverse effect on public health and no large number of disease deaths. However, the event brought increased interest in finding a solution for the city’s sewage problem. It was only a few years later before the authorization of a sanitary canal in 1889, and the start of construction in 1892.

A permanent solution was sought and in 1889,44 by an incredible margin of 99%,45 the voters approved the formation of The Sanitary District of Chicago, covering the City and a few outside areas including Oak Park. The solution proposed by the District was to create a drainage canal reversing the flow of the Chicago River. Waste and sewage, still totally untreated, would flow away from the lake, over the continental divide and into the Illinois River Valley. Chicago called it "disposal by dilution."46

The idea was simple; with such a flat slope, it would only be necessary to cut a channel to a point in the Des Plaines valley below the level of Lake Michigan and the water would flow. It would prove to be a massive excavation project to cut to the depth required, much of it through bedrock. Along the way, the idea had been expanded to include a greatly improved waterway, capable of handling the big boats of the Great Lakes. The cut was 200 feet wide, 20 feet deep, and required 40 million cubic feet of excavation. Only a single lock was required -- a 34' high control structure at Lockport. The lock at Lake Michigan was added later. The canal connected to the Chicago River at Bridgeport and joined the Des Plaines River just above Joliet, a length of only twenty-eight miles, a quarter of the length of the I&M. This was because of the much greater flow of water allowed the rivers below Joliet to be made navigable.

Plans were completed in 1889,47 and work was begun with much celebration on "Shovel Day," September, 3, 1892.48 The concept of reversing a river--making it run uphill--was compared to Hercules cleaning of the Augean Stables. It caught the imagination of everyone and drew worldwide attention. Generally the reaction was favorable. Even downstate communities such as Joliet and Ottawa, Illinois looked forward to the new canal. After years of living with the sluggish flow of sewage in the I&M Canal, the Sanitary Canal was to bring a great improvement in water quality.

Only St. Louis resisted. Day after day, negative articles and critical editorials filled that city's local newspapers, arguing against "this filthy nuisance."

As the time of completion and opening of the canal approached, word leaked that St. Louis and the State of Missouri intended to file for an injunction to stop the canal.49 The Sanitary District raced to complete the work. Reasoning that the flow of water would be hard to stop once it was started, on January 2, 190050, two weeks before the official opening, and without proper permits, the Sanitary District Board quietly ordered a needle dam knocked down, which turned the water of the Chicago River into the newly dug channel of the canal. Two weeks later, now with all permits in hand, the control works at Lockport were opened. The Great Lakes flowed unimpeded into the Mississippi River basin again for the first time in 12,000 years.51

The canal was a great success. Lake Michigan water quality improved with an immediate decrease in disease rates. Downstate, the situation improved as well. Independent tests conducted by Scientific American Magazine showed that oxygenation from the increased quantity of fresh water cleansed the water and made it safe.52

But controversy continued, mostly over flow rates and the amount of water that could be taken from Lake Michigan. Lawsuits by contiguous states, international protests by Canada, Congressional legislation and Presidential vetoes53 all ensued. Allowable flow rates were alternately raised and lowered, finally settling on 3,200 cubic feet per second. 

Improvements in the 20th century include a control lock at the mouth of the Chicago River and Deep Tunnel to temporarily hold storm surges. Most importantly new treatment facilities are being added. Essentially since 1950, all water in the canal has been fully treated.54

In reversing the flow of the Chicago River, the Continental Divide no longer functions as it did historically. The water still divides in Oak Park, but all water runs to the Gulf.


Bill Dring, author
Written June 1998. Revised November 2002, January 2007, and December 2020. Revised October 2021 by Deborah Mercer.

All maps designed by Dennis McClendon, Chicago Cartographics


For more information on the Continental Divide, follow this link to our webpage.

For more information on the Chicago Portage, follow this link to our webpage.

For more information on the I&M Canal, follow this link to our webpage.

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