When Chicago Reversed Its River: Engineering Maps of an Impossible Feat
On January 2, 1900, workers opened the controlling gates of the Chicago Sanitary and Ship Canal at Lockport, Illinois, and the Chicago River, which had flowed east into Lake Michigan for thousands of years, began flowing west. It was an act of engineering audacity that literally reversed a river, rerouted a continental watershed, and solved one of the most deadly public health crises in American history. The maps that documented this project, from the initial survey drawings of the 1880s to the as-built engineering plans of 1900, constitute one of the most technically impressive chapters in Chicago's cartographic record and tell a story in which sewage, cholera, politics, and ingenuity intersect on every sheet.
The Problem: A City Poisoning Its Own Water Supply
To understand why Chicago reversed its river, you must understand the city's relationship with water. Chicago sits on the southwestern shore of Lake Michigan, and from its founding, the city drew its drinking water from the lake. The Chicago River, which originally flowed east from the interior into the lake, served simultaneously as the city's primary sewer. The result was grimly predictable: untreated sewage dumped into the river flowed into the lake and contaminated the drinking water supply.
The consequences were catastrophic. Cholera epidemics struck Chicago repeatedly in the 1850s and 1860s, killing thousands. Typhoid fever was endemic. In 1854, a particularly severe cholera outbreak killed roughly six percent of the city's population. The city responded by extending its water intake pipes farther into the lake, building new pumping stations, and eventually constructing the two-mile-long Lake Michigan Tunnel in 1867, which drew water from a crib two miles offshore. But the city kept growing, the river kept carrying more sewage, and the contamination plume in the lake kept expanding. By the 1880s, it was clear that no amount of pipe extension could solve the fundamental problem: the river was carrying the city's waste directly into its water supply.
Key Dates in the Water Crisis
- 1854: Cholera epidemic kills approximately 1,424 Chicagoans, roughly six percent of the population
- 1855: City engineer Ellis Chesbrough proposes raising the grade of city streets and installing a sewer system draining into the river
- 1867: Completion of the Lake Michigan Tunnel, extending the water intake two miles offshore
- 1871: Great Fire destroys much of the sewer infrastructure, compounding the public health crisis
- 1879: Severe rainstorm flushes river water past the offshore water intake cribs, causing a spike in waterborne disease
- 1885: A catastrophic storm sends a massive sewage plume to the water intake cribs, killing approximately 90,000 people from cholera and typhoid over the following years, according to some estimates
- 1889: Creation of the Sanitary District of Chicago, charged with solving the problem permanently
The Solution: The Sanitary and Ship Canal
The solution that Chicago's engineers devised was breathtaking in its simplicity and ambition: dig a canal large enough to reverse the flow of the Chicago River, sending the city's wastewater away from Lake Michigan and toward the Des Plaines and Illinois rivers, which drain into the Mississippi and ultimately into the Gulf of Mexico. The canal would need to be deep enough and wide enough to create a current sufficient to pull the river's flow westward, overcoming the natural eastward gradient, however slight, that had carried the river to the lake for millennia.
The Sanitary District of Chicago, established by the Illinois legislature in 1889, was given the authority and the taxing power to execute this plan. The chief engineer, Isham Randolph, oversaw a project that at its peak employed more than 8,500 workers. The canal, officially named the Chicago Sanitary and Ship Canal, ran 28 miles from the south branch of the Chicago River at Robey Street (now Damen Avenue) to Lockport, Illinois, on the Des Plaines River. It was 24 feet deep, 202 feet wide at the top, and 110 feet wide at the bottom, dimensions that made it one of the largest earth-moving projects in history, exceeding even the Panama Canal in the volume of earth and rock removed.
The Engineering Survey Maps
The cartographic record of the Sanitary and Ship Canal is extraordinary in its scope and technical detail. The project generated thousands of individual map sheets, survey drawings, cross-sections, and engineering plans that document every phase of the work from initial reconnaissance to final construction.
The earliest maps in the series, dating from the mid-1880s, show the proposed route of the canal overlaid on existing topographic surveys of the Des Plaines River valley. These reconnaissance maps identify the geological formations that the canal would need to cut through, including the Niagaran dolomite, a hard limestone bedrock that would require blasting rather than simple excavation. The geological sections that accompany these maps, showing cross-cuts of the earth and rock layers at intervals along the route, are among the most technically sophisticated cartographic documents produced in nineteenth-century Chicago.
Types of Engineering Maps Produced
- Route survey maps: Showing the proposed canal alignment in relation to existing topography, roads, railroads, and property boundaries
- Geological cross-sections: Detailed drawings showing the earth and rock layers at measured intervals along the canal route
- Hydraulic flow diagrams: Maps showing the pre-reversal and post-reversal water flow patterns of the Chicago River and Des Plaines River systems
- Construction progress maps: Updated regularly during the eight years of construction, showing completed and in-progress sections
- Property acquisition maps: Identifying the parcels of land that the Sanitary District needed to acquire for the canal right-of-way
- Lock and control works plans: Detailed engineering drawings of the structures that would regulate water flow at Lockport and other points along the canal
Before and After: Water Flow Maps
Among the most visually dramatic documents in the canal's cartographic record are the before-and-after water flow maps. Pre-reversal maps show the natural drainage pattern of the Chicago area: the Chicago River flowing east into Lake Michigan, the Des Plaines River flowing southwest into the Illinois River, and the low, marshy continental divide between them, the same divide that had made the Chicago portage possible since prehistoric times. Post-reversal maps show the new pattern: the Chicago River flowing west through the canal into the Des Plaines, with Lake Michigan water being drawn into the river system to dilute the sewage and maintain the westward current.
These flow maps typically use arrows or color coding to indicate the direction and volume of water movement. Some of the more detailed versions include flow rate data, showing the volume of water moving through the canal at various points and the corresponding reduction in sewage concentration. The before-and-after comparison is striking: what had been a natural watershed boundary, the low ridge between the Great Lakes and Mississippi drainage systems, simply ceased to exist as a hydrological reality. Water that would naturally have ended up in the Atlantic Ocean via the Great Lakes and St. Lawrence River was now being diverted to the Gulf of Mexico via the Mississippi.
The Legal Battles: Maps in Court
The reversal of the Chicago River did not just rearrange hydrology; it rearranged politics. The state of Missouri and the city of St. Louis, which drew their drinking water from the Mississippi River downstream of the point where Chicago's diverted sewage would eventually reach, were furious. In 1900, Missouri filed suit against the state of Illinois in the United States Supreme Court, arguing that the canal would contaminate St. Louis's water supply with Chicago's sewage.
The case, Missouri v. Illinois, produced its own body of cartographic evidence. Both sides submitted maps showing the canal route, the river systems involved, the distances between Chicago and St. Louis, and the projected dilution of sewage over those distances. Missouri's maps emphasized the directness of the hydrological connection between Chicago's sewers and St. Louis's water intake. Illinois's maps emphasized the enormous volume of water in the Mississippi and the vast distance, more than 300 miles, over which the sewage would be diluted before reaching St. Louis. The Supreme Court ultimately ruled in Illinois's favor in 1906, finding that Missouri had not demonstrated sufficient evidence of harm, a decision that was influenced in part by the cartographic and scientific evidence presented.
How the Reversal Changed Regional Cartography
The reversal of the Chicago River had consequences for cartography that extended far beyond the canal itself. Maps of the Great Lakes watershed had to be updated to reflect the diversion of water from Lake Michigan into the Mississippi basin. Navigation charts of the Illinois River and the upper Mississippi were revised to account for the increased water volume. And maps of Chicago itself were updated to reflect the new reality that the river in the heart of the city now flowed in the opposite direction from what every previous map had shown.
The canal also opened a new shipping route connecting the Great Lakes to the Mississippi River system, fulfilling the vision that Louis Jolliet had articulated in 1673 when he proposed a canal across the Chicago portage. Navigation maps of the new waterway were produced by the Sanitary District and by the U.S. Army Corps of Engineers, showing channel depths, lock dimensions, bridge clearances, and docking facilities. These navigation maps, updated regularly throughout the twentieth century, document the evolution of the canal from a sanitary project to a commercial shipping corridor. Our article on the earliest known map of Chicago traces how Jolliet first envisioned this connection.
At Earliest Chicago Maps, we carry reproduction prints of several of the most significant canal-era engineering maps, including route surveys, hydraulic flow diagrams, and the dramatic before-and-after water flow comparisons. These documents make compelling display pieces for engineering firms, water agencies, and anyone fascinated by the intersection of infrastructure and cartography. Our authentication team can also assess original canal-era documents. Explore this chapter of Chicago's history through our Chicago Timeline Explorer.
