Which U.S. city is famous for dyeing its river green for Saint Patrick’s Day? Chicago is famous for the tradition.
Chicago’s annual river-dyeing ceremony turns part of the Chicago River bright green before Saint Patrick’s Day celebrations. Crowds gather downtown to watch boats release the dye, followed by one of the city’s major parades.
The custom began accidentally in 1961, when plumbers used fluorescein dye to trace pollution entering the river. The idea was adopted as a holiday spectacle, and the Chicago Journeymen Plumbers Union became closely associated with carrying it out. The event is commonly dated to 1962 as an organized tradition.
Environmental concerns later led organizers away from fluorescein. Today’s mixture is described as a vegetable-based dye, and the exact formula is kept secret. Chicago’s ceremony inspired other green-water displays, including green fountains at the White House in 2009.