What makes the Chicago River so green on St. Patricks Day? According to ABC 7 Chicago, its just a food dye that keeps the river green for 24 to 48 hours. The interesting thing about this dye is that it is concocted by The Chicago Plumbers Union Local 130.
For 55 years the plumbers have been making the dye that causes no damage and gives us all something to take pictures in from of on St. Patricks Day. The dye is then mixed, often by boats and one year even by a jet pack. This year, St. Patricks Day will fall on a Saturday so expect big crowds at the annual river dying at 9AM!
