Chicago has a long history of celebrating St. Patrick’s Day, but it is best know for adding dye to the Chicago River which flows through the city every year.  The city usually does this a few days before St. Patrick’s Day, to allow for the water to stay green throughout the festivities.

The dying of the river actually happened originally by accident, when plumbers used fluorescein dye to trace sources of illegal pollution discharges.  It eventually became tradition, but the Environmental Protection Agency eventually stepped in and determined fluorescein to be detrimental to the river’s health.  Today the local plumbers union colors the river green with 40 pounds of vegetable dye, which is non-toxic and allows for the tradition to continue.

The Obama’s have carried this tradition from their hometown of Chicago to the fountains of the White House, where they are also dyed yearly.

Enjoy this time lapse view of the process from high above the river by filmmaker Peter Tsai.

Michael Cuffe for Warholian