St. Patrick's Day

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The origins of Chicago's "green" river

Shades of green are everywhere on St. Patrick's Day. But arguably no green is more distinctive come Patty's Day than the green flowing water of the Chicago River, which is dyed green each year in honor this beloved holiday.

A series of natural and manmade rivers and canals with a combined length of 156 miles, the Chicago River runs through the city of Chicago, Ill., including its center. Today the river is comprised of the Main Stem, North Branch and the South Branch, which gets much of its water from Lake Michigan. The river has long been a center of industrialized operations, helping to foster trade to Illinois and other areas of the midwest. The Chicago River is also a tourist destination that takes on a new persona each season in late winter, when it becomes "green" and serves as the centerpiece of St. Patrick's Day festivities in the Windy City.

On the weekend closest to St. Patrick's Day, workers add 40 pounds of powdered green vegetable dye into the water to turn the river green. The dye takes some time to dissipate, but eventually the river runs green in honor of St. Patrick. Dyeing the river green has been a tradition for more than 40 years, and it's a tradition that actually arose out of a fluke discovery.

In 1961, Stephen Bailey was speaking with a fellow plumber and noticed the plumber's white coveralls were stained Kelly green. Bailey inquired as to how the coveralls got so green, and it was discovered that a fluorescein dye used to detect trace sources of illegal pollution being discarded into the river water was responsible. Bailey wondered if this dyeing of the water could become an annual tradition in honor of St. Patrick's Day and set forth a plan to achieve just that.

The United States Environmental Protection Agency has since outlawed the use of fluorescein for this purpose, since it has been shown to be harmful. Now the St. Patrick's Day Parade committee uses the vegetable dye, which is believed to be much safer. Because of connecting waterways, it is feasible that the green water of the Chicago River can flow into the Illinois River, to the Mississippi River, then out into the Atlantic gulf stream, and finally to the Irish sea. While it is unlikely the green hue would remain, perhaps with some leprechaun magic, a green water highway could truly connect Chicago to Ireland.

Various cities have tried to emulate the green river, but have not been able to achieve the same, vibrant green as Chicago. The dye mixture is a closely guarded secret. In 2009, First Lady Michelle Obama, a Chicago native, requested that the White House fountains be dyed green to celebrate St. Patrick's Day and perhaps bring a touch of home to Washington, D.C.