Environmental History & Challenges - Chicago's industrialization in the 19th century led to severe pollution of the Chicago River with industrial waste, meat packing byproducts, and raw sewage, threatening the city's drinking water source, Lake Michigan [5][6] - In the 1890s, Chicago reversed the flow of the Chicago River by constructing the Chicago Sanitary and Ship Canal, diverting water westward towards the Mississippi River [7][8] - Chicago constructed a wastewater treatment system, considered one of the seven wonders of American engineering in 1955, but initially, the treated water was still unsuitable for most indigenous fish species [9][10] Ecological Redemption & Urban Development - By the mid-20th century, only 10 fish species survived in the Chicago River [11] - Mayor Richard J Daly aimed to enhance Chicago's reputation and envisioned a wild, sustainable salmon population in the Chicago River, even suggesting businessmen could fish during lunch breaks [12][18] - The Clean Water Act of 1972 led to improved water quality, and by 1982, Chicago stopped using chlorine in wastewater treatment, resulting in the return of fish species [23][24] Biodiversity & Future Outlook - Currently, 58 fish species inhabit the Chicago River, and other animals like river otters, beavers, deer, foxes, coyotes, and even bald eagles have returned to the area [24][25][26] - The industry emphasizes the importance of remembering past environmental mistakes while continuing to make conscious decisions to improve the ecological health of the environment for all species [27][28]