On Saturday, March 14, 2026, at 10:00 AM local time, the Chicago River was dyed its signature emerald green, marking the 64th anniversary of the city’s annual St. Patrick’s Day event. The operation drew large crowds to the downtown area and preceded the city’s scheduled holiday parade. The practice is organized, funded, and guarded entirely by the Chicago Journeymen Plumbers Local Union 130, which handles the logistics of the rapid water transformation.
The visual shift is accomplished using two motorboats working in tandem along the waterway. One boat dumps approximately 40 pounds of an eco-friendly, vegetable-based powder into the river, while a second boat follows closely behind to churn the water, activating the dye in a matter of minutes. Curiously, the powder itself is orange and only turns bright green once it reacts with the surface water. The peak vibrant hue typically lasts for four to five hours, though faint traces of the tint remain visible for a few days for those engaging in weekend travel along the river walk.
The tradition originated in 1962 following an observation by Stephen Bailey, the union’s business manager at the time. In 1961, Bailey noticed bright green stains on a plumber’s white overalls, which were caused by a fluorescent dye originally used to detect sewage leaks in the city’s pipe infrastructure. With the support of then-Mayor Richard J. Daley, the union utilized a similar dye to color the river for the holiday. Following environmental concerns, the original oil-based formula was replaced in 1966 with the current non-toxic powder. The exact recipe for the modern dye remains a closely guarded union secret.