The question of whether Chicago is built upon a swamp is rooted in geographical reality. The area was not an impenetrable, dense swamp, but a low-lying, poorly drained landscape influenced by water. The city’s foundation is linked to the immense effort required to transform this waterlogged terrain into a functional metropolis. This struggle against nature resulted in dramatic civil engineering projects of the 19th century, forever changing the course of the city.
Defining the Pre-Urban Landscape
The physical character of the Chicago region was directly shaped by the retreat of the Wisconsin glaciation approximately 14,000 years ago. This glacial meltwater dammed up, creating Glacial Lake Chicago, whose flat, low-lying bed became the foundation of the modern city. The result was the Chicago Lake Plain, a vast area with virtually no topographical variation and heavy clay soils that prevented efficient drainage.
Before settlement, the landscape was a mosaic of interconnected ecosystems, including marshes, sloughs, and wet prairie. Wet prairie, characterized by grasses like prairie cordgrass, grew in poorly drained areas where the water table was consistently near the surface. The highest point on this plain, the continental divide, was only 10 to 17 feet above Lake Michigan. This low elevation made the entire area prone to standing water and slow runoff, presenting an immediate obstacle to urban development.
Early Settlement Challenges and the Need for Drainage
The flat, waterlogged topography created immediate and severe problems for the nascent settlement. The ground was unable to absorb waste, leading to streets that quickly became impassable quagmires, earning the city the nickname “Mud Hole of the Prairies”. Sewage, which was initially dumped into the Chicago River, flowed sluggishly toward Lake Michigan, which was also the city’s source of drinking water.
This contamination created a public health catastrophe, as the city’s waste mixed with its water supply. The resulting sanitation crisis led to repeated outbreaks of waterborne diseases, including typhoid fever and cholera. A major cholera epidemic in 1854 killed an estimated six percent of the city’s population, forcing officials to recognize that the land’s natural drainage limitations required a radical solution. The city’s survival depended on imposing an artificial gradient where none naturally existed.
The Grand Engineering Feats Raising the City and Reversing the River
To address the drainage and sanitation crisis, Chicago embarked on two unprecedented civil engineering projects that physically reshaped the city. The first was the wholesale raising of the city’s street grade, a massive undertaking that began in the 1850s. Engineers devised a plan to install a comprehensive sewer system that required gravity-fed drainage, necessitating that the entire city be lifted between 4 and 14 feet.
Crews used thousands of jackscrews to physically jack up hundreds of buildings, including occupied masonry structures weighing up to 35,000 tons. The Lake Street row of stores, for example, was raised nearly five feet in one go, with businesses continuing operations inside. After a building was raised, the land beneath was filled with soil to the new grade, allowing for the construction of an underground sewer network. This effort successfully removed the city from the worst of the mud and standing water, but the sewage still flowed into the Chicago River and discharged into Lake Michigan.
The second project was the reversal of the Chicago River’s flow, designed to permanently move the city’s sewage away from the lake. In 1889, voters approved the formation of the Sanitary District of Chicago (now the MWRDGC) to construct the Chicago Sanitary and Ship Canal. Completed in 1900, the 28-mile-long canal cut through the continental divide, forcing the Chicago River to flow backward into the Des Plaines River, part of the Mississippi River watershed. This feat of engineering, which involved the largest earth-moving operation in North America at the time, protected the city’s drinking water supply and enabled Chicago’s continued growth.
Ecological Legacy and Modern Restoration
The centuries of engineering to drain and elevate the land resulted in the near-total eradication of the native wetland and wet prairie ecosystems. Historically, over 90% of Illinois’s wetlands were drained or filled for agriculture and development, a trend that was particularly aggressive in the Chicago region. However, modern environmental science recognizes the value of these former landscapes, particularly for their functions in flood control and biodiversity.
Today, efforts focus on restoring the remnants of the original ecosystems, primarily in the Calumet region on the city’s southeast side. Conservation groups are working to restore hundreds of acres of marsh and wet prairie, recognizing their role in supporting high biodiversity. Projects like the restoration of the Powderhorn Prairie and Marsh Nature Preserve aim to alleviate flooding for surrounding communities. They achieve this by reestablishing the land’s natural water-holding capacity, linking Chicago’s hydrological history to a future focused on ecological resilience.