It's one of Chicago's most recognizable and iconic traditions, with crews taking to boats and dyeing the Chicago River a gorgeous shade of green in honor of St. Patrick's Day.
That tradition, adhered to for decades, will continue this year thanks to the efforts of Chicago Journeymen Plumbers Local 130, and will coincide with the city's annual St. Patrick's Day parade.
According to officials, the river dyeing this year will take place on Saturday, March 16 at 10 a.m., just one day before the St. Patrick's Day holiday.
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 decades, with this year marking 63rd time they've done so.
Officials do remind the public that the lower level of the riverwalk will be closed on that date, with no access available via public stairwells in the area. Instead, revelers are asked to watch the festivities on Upper Wacker Drive, with the best views available between Columbus and Fairbanks.
The St. Patrick's Day Parade will begin at approximately 12:15 p.m. on March 16, with route information to come. Typically, the route moves along Columbus Drive from Balbo to Monroe Street, allowing access to numerous downtown attractions before and after the parade.
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How Do They Dye it Green?
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For those who have never seen the process in person, each year the Chicago Plumbers union embarks on boats that putter along the Chicago River, with a rather curious concoction that sprays dye out of plumping pipes and spout pumps.
But the mysterious mixture doesn't come out green.
"If you were watching this for the first time you would think this is a mistake or a bad joke," the post goes on to say. "You see the dye is orange, and its initial color on the surface of the river is orange, and you would think to yourself what 'heathen would do something like this.'"
However, once the dye sets in, the color in a stroke of luck changes to green, and the "true color magically appears," the union says.
WATCH: Behind the Scenes: Creating Chicago's Iconic Green River Dye
According to Local 130, other cities have attempted similar feats, but never found success. It's that, the union says, and the magical color transformation that perhaps plumbers may have had some additional help with.
"We believe that's where the Leprechaun comes in," Local 130 says.
"As the late Stephen Bailey has said, the road from Chicago to Ireland is marked in green," the post regales. "From the Chicago River to the Illinois River, then to the Mississippi, up the Gulf Stream and across the Atlantic you can see the beautiful green enter the Irish Sea, clearly marking the way from Chicago to Ireland."
What's in the Dye?
Sorry to say, we don't have an exact answer, and we won't get the secret from the plumbers' union themselves.
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.
Why Do They Dye the River Green?
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!"
And there you have it.