The Chicago River, in Illinois, is dyed green each year in celebration of St. Patrick’s Day. The tradition dates back to 1962 when sewer workers spilled green dye into the river to check for sewer discharges. The idea to turn the river green for Saint Patrick’s Day was born. Originally, 100 pounds of vegetable dye was used to turn the river green for a whole week. That proved to be a bit much and now, only forty pounds of dye is used and the color only lasts for several hours.

Other celebrating cities include Indianapolis, Indiana, who dyes its main canal green and Savannah, Georgia dyes its downtown city fountains green.