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st. patrick's day parade 2018
Photograph: Grace DuVal

How and why the Chicago River is dyed green for St. Patrick’s Day

We found out how many plumbers it takes to turn the Chicago River green for St. Patrick’s Day.

Zach Long
Written by
Zach Long

Before the annual Chicago St. Patrick’s Day Parade steps off in Grant Park each March, representatives of the Chicago Journeymen Plumbers Local Union 130 have an important job to do: turning the Chicago River a vibrant shade of green. Thousands of onlookers show up to take in the annual spectable, lining sidewalks, bridges and the Chicago Riverwalk (or buying tickets to viewing parties on nearby rooftops).

Before you watch the city's major waterway transform, you can learn about how this unnatural phenomenon is accomplished each year. We spoke with Plumbers Union recording-secretary Patrick McCarthy, who was able to reveal a few (but not all) of the secrets behind the Chicago River dyeing process.

RECOMMENDED: Your guide to St. Patrick's Day in Chicago

Why is the Chicago River dyed green?

When Richard J. Daley was mayor of Chicago, he wanted to turn Lake Michigan green in honor of St. Patrick's Day. He was persuaded to dye the more manageable Chicago River instead, with the same green dye plumbers used to find sewage leaks.

When did Chicago begin its annual river-dyeing tradition?

The dyeing dates back to 1962 and has always been performed by the Chicago Journeymen Plumbers Union.

What length of the river is dyed?

A quarter mile of the waterway, stretching from Columbus Drive to State Street.

How many boats are used to dye the river?

Two boats—one to drop the dye in and another to stir it up.

How long does the dye last?

At least a day, but sometimes two to three days if there’s no wind or rain.

What’s in the dye?

The exact formula is a secret, but it’s an orange-red, vegetable-based powder.

Who operates the boats?

Eight people in all, including members of the Butler and Rowan families, who originated the tradition.

How much dye is dumped into the river?

Forty pounds over the course of about 45 minutes.

How messy is the dyeing process?

Very. The folks who dye the river are usually washing dye out of their hair for a couple of weeks.

Has the Chicago River been dyed for any other ocassions?

Shortly after the Chicago Cubs won the World Series in 2016, the Chicago Journeymen Plumbers Union dyed a portion of the Chicago River blue.

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