Chicago River reopens for swimming after 100 years of pollution closure

For almost a century (99 years), the Chicago River in Illinois stood as a symbol of water pollution, rendered unfit for recreational use. 

Now, the city has announced the return of an open-water swimming competition in the river, the first in nearly 100 years, scheduled for Sunday, September 21, 2025, with more than 500 participants expected. 

The event marks a milestone in Chicago’s environmental restoration and conservation efforts.

The last time swimming in the Chicago River was officially permitted was in 1926. Decades of unchecked pollution, including industrial waste, household sewage, and garbage, soon earned it the reputation as one of America’s dirtiest rivers throughout the 20th century.

A history of pollution

In the late 19th century, sections of the river such as Bubbly Creek became notorious as dumping grounds for slaughterhouses and meatpacking plants in the Union Stockyards. 

Blood, entrails, and animal carcasses were discharged directly into the water, producing methane and hydrogen sulphide gases that bubbled constantly from the riverbed, making it appear as if the water was boiling. The name “Bubbly Creek” vividly reflected its foamy, foul-smelling surface.

Breweries, sawmills, and brick factories also contributed to the contamination, turning the river into an “open sewer” that threatened Lake Michigan, the city’s main source of drinking water.

At the time, politicians, engineers, and public health experts believed reversing the flow of the river through the construction of the Chicago Sanitary and Ship Canal in 1900 would solve the crisis by diverting wastewater away from Lake Michigan and into the Illinois River.

Yet by 1906, the river remained heavily polluted. Author and social reformer Upton Sinclair, in his groundbreaking novel The Jungle, described the Chicago River as a “great open sewer” that reeked like “hell’s pit” and through which no breath of fresh air could pass.

Reversing the river (1900)

To prevent factory wastewater from contaminating Lake Michigan, Chicago reversed the river’s flow in 1900, directing water away from the lake and constructing the Chicago Sanitary and Ship Canal. The project was hailed as one of the engineering marvels of the 20th century.

Later, in 1980, the Tunnel and Reservoir Plan (TARP) was launched. This massive underground system was designed to capture stormwater and sewage, preventing it from spilling directly into the river during heavy rainfall.

The Clean Water Act

Since the 2000s, the Chicago River restoration has shown visible progress under the Clean Water Act. New wastewater treatment systems were built, riverfront areas rehabilitated, and public awareness campaigns promoted environmental stewardship. 

Collaboration between government agencies, the city, and non-profit organisations has improved water quality to internationally recognised standards.

In 2025, city health authorities confirmed the river’s water quality as safe for open-water swimming, a turning point for Chicago. Today, the river is home to nearly 70 species of fish, along with beavers and turtles.

Chicago Mayor Brandon Johnson hailed the return of the historic swim as a landmark victory for both the city and the river itself: “This is not only a triumph for Chicago, but also for the Chicago River, which once served as an industrial backwater but now stands proudly as the city’s swimming pool.”

Chicago River Swim 2025 set to make history in September

The Chicago River Swim 2025 will see more than 500 swimmers take on a course of over one mile through the heart of downtown Chicago, marking the river’s first official open-water swim in nearly a century. The event, scheduled for Sunday, September 21, 2025, will welcome both professional and amateur athletes, though only those with prior open-water experience, such as triathletes, professional swimmers, or Olympians, are eligible. Recreational swimmers are excluded.

Strict safety measures will be in place, including daily water-quality testing, on-site paramedics, and rescue teams. More than 100 safety personnel, including 40 lifeguards, will patrol the course using kayaks, paddleboards, jet skis, and motorboats. 

Every participant will wear a GPS tracker, while the US Coast Guard will close the stretch of the river to other vessels during the race.

The course begins at Dearborn Street Bridge, heading east to State Street, looping back west to Lake Street, and finishing near Clark Street Bridge. Participants can choose between 1-mile and 2-mile distances.

Spectators will gather along the Riverwalk between Lake and Clark Streets, which will be transformed into a lively viewing area with food, drinks, and VIP events.

More than a race

Organisers emphasise that the swim is not just a competition but a celebration of the river’s revival and the success of Chicago’s decades-long environmental restoration.

The event also serves as a fundraiser, with all proceeds supporting ALS research at Northwestern University, swimming lessons for underprivileged youth, and initiatives to reduce racial disparities in access to swimming.

US Olympic bronze medallist Natalie Hinds, who will join the race, said: “I care deeply about water safety, expanding opportunities to learn to swim, and preventing drownings through education and community engagement.”

However, officials have stressed that the race will only proceed if daily water tests confirm safe bacteria levels. If standards are exceeded, the event could be postponed or cancelled for safety reasons.