In what is one of Chicago's hallmark annual traditions, the Chicago River was dyed green Saturday morning in celebration of St. Patrick's Day as hundreds of onlookers watched the water transition into a bright emerald.
The iconic event, operated by Plumbers Union Local 130, kicked off Chicago's St. Patrick's Day festivities.
Typically, the dyeing of the Chicago River occurs the Saturday before St. Patrick's Day and coincides with the city's with the St. Patrick's Day Parade.
Weather conditions for the river dyeing have wildly varied in the past as March weather in Chicago is often a wild card, and Saturday was no different.
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The hundreds of spectators for the event braved the cold, with the river turning green beneath gloomy skies in near-freezing temperatures.
The Chicago Plumbers Union, Chicago Journeymen Plumbers Local 130, says its been dyeing the Chicago River green in honor of the city's St. Patrick's Day celebrations for nearly 68 years.
And the specific green color, the union says is "identical to the greens of Ireland from where it got its name, The Emerald Isle."
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The story goes, in 1961, a man by the name of Stephen Bailey -- the business manager of the plumbers union -- was approached by "one of his plumbers who was wearing some white coveralls," a post by Local 130 says. It was then the union says, that Bailey noticed the overalls had been stained or dyed with "a perfect shade of green," or "an Irish green to better describe it."
When wondering how the coveralls could have turned such a tint, the tale continues, Bailey and his plumbers discovered that it was from to the dye used to detect leaks in the river.
"That's when Mr. Bailey bellowed," the Union declares, "Call the mayor ... we will dye the Chicago River green!"
As far as what's inside the dye, it's safe to say we'll never know.
The plumbers union, Choose Chicago says, "still holds the river-dyeing honors today." But you won't be able to find their recipe anywhere. "Their environmentally friendly dye formula remains a closely kept secret," Choose Chicago says.