Every March, to celebrate St. Patrick’s Day in the city, the Chicago River is dyed a brilliant green in front of thousands of spectators. This tradition began in the 1960s, when green dye was used to better identify the source of leaky pipes in the city. The following year 100 pounds of dye was used to mark St. Patrick’s Day. The dye is environmentally friendly and vegetable-based, ensuring the river does not get polluted.

This year, the 64th annual river-dyeing took place the Saturday before St. Patrick’s Day, on March 14 in downtown Chicago at 10 a.m. It was packed with thousands of curious residents and visitors who watched the process from beginning to end. Boats, including those from the Architecture Tour— the particular company which is often seen taking tourists on boat tours around the city— poured 40 pounds of powdered dye into the river through hoses. Interestingly enough, the vegetable-based dye initially appears orange before turning green as it spreads through the water. The dyeing could be seen from areas throughout downtown and along the river, such as Upper Wacker and several bridges, although people were also able to book a cruise with City Cruises to gain a more exclusive view of the dyeing in real-time ahead of the event.

After the river dyeing, viewers could watch Chicago’s annual St. Patrick’s Day Parade on Columbus Drive. The parade, which began in 1956, is one of the largest in the United States and always takes place the same day as the river dyeing to commemorate St. Patrick’s Day. Another parade, the South Side Irish Parade, was held the next day on Western Avenue. Chicagoans were able to drop into one of the many riverfront restaurants and bars during or after the river-dyeing where St. Patrick’s Day was celebrated.

While the eco-friendly emerald hue in the Chicago River has likely faded by now, there is always an opportunity to see the bright green of the river next year.