On March 17, millions of Irish Americans will celebrate St. Patrick’s Day by wearing green. But the city of Chicago, Illinois, takes the tradition a giant step further. Since 1962, it has dyed the Chicago River green! Before the city’s annual St. Patrick’s Day Parade, workers in boats dump about 40 pounds of a harmless dye into the river. People pack the streets along the river to see the bright-green coloring before it disappears a day or two later.