Dyeing of the Chicago River

In what might be one of the world’s most famous St. Patrick’s Day rituals, 45 pounds of eco-friendly vegetable dye are poured into the Chicago River to turn it emerald green for the occasion. Actually, at first glance, the dye appears orange on the river’s surface—but don’t panic. Thanks to a little leprechaun magic (or, well, science), the hue transforms and seeps in until the whole river is a bright, beautiful green.

The dyeing of the river remains a beloved tradition for many generations of Chicagoans (it dates back over 50 years ago) and draws nearly 400,000 spectators downtown looking to catch a glimpse before taking in the parade that follows. The Chicago River keeps its coloring for about five hours only, so don’t miss out.