The Chicago River dyeing is a cherished annual tradition marking St. Patrick’s Day, where the river is transformed into a vibrant green. This year, the event took place on Saturday, March 15, 2025, starting at 10 a.m.
The practice began in 1961 when members of the Chicago Journeymen Plumbers Union Local 130 used fluorescein dye to trace illegal pollution discharges, inadvertently turning the river green. Embracing the festive accident, they initiated the tradition, now using a secret, environmentally friendly vegetable-based powder.
Spectators gathered along the riverbanks and bridges to witness the transformation, which lasts for several hours. The event is followed by the annual St. Patrick’s Day parade, celebrating Irish culture and heritage.
If you missed this year’s dyeing, mark your calendar for March 14, 2026, when the river will once again turn green in celebration of St. Patrick’s Day.