The Chicago River, once considered one of the dirtiest urban waterways, has seen significant improvements in water quality since the passage of the Clean Water Act in 1972. While organized swimming hasn’t been authorized in over a century due to ongoing concerns about combined sewer overflows, an upcoming event aims to showcase the river’s progress and highlight the importance of ongoing cleanup efforts. The organizers emphasize strict safety measures and will monitor water quality data in the lead-up to the event, scheduled for September, Chicago’s driest month. However, some experts caution that heavy rains and a large urban population can still contribute to dangerous conditions, and swimming should be avoided following heavy rainfall or overflows.