The Windy City Celebrates Its Annual Green Dyeing of the Chicago River for St. Patricks Day

Jen Juneau
Updated
"The dye that we use is a leak detection dye that we use in plumbing pipes," St. Patricks Day Parade Coordinator Pat McCarthy told ABC 7 Chicago

Chicagosnew hue is to dye for.

On Saturday, theChicago Journeymen Plumbers Union took to the Chicago River for its annual green-tinting event, pouring dye into the waters to celebrate the upcoming St. Patricks Day.

Thousands of people gathered for the festivities, which also includes a paradeand Irish-themed food and drinks offered by various vendors along the Chicago Riverwalk.

One boat drops the dye into the water and its an orange powdery substance and its completely environmentally safe, parade coordinator Pat McCarthy told ABC 7 Chicago. Once the orange powder hits the water, it turns a vibrant green and the second boat follows and stirs it up to make sure that that dye spreads out.

The tradition of dyeing the river green dates all the way back to 1961, and involves a product that the city just kind of came across naturally.

The dye that we use is a leak detection dye that we use in plumbing pipes and apparently there were a couple guys doing it a lot one day, McCarthy said.

They came to the union hall and the business manager saw them covered in green and he got the idea, I wonder if we put it in the river, would the river stay green?

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Countless people took to social media to spread their joy about the event, some even captioning videos from their spots high above the 156-mile-long river.

When you get to treat yourself to a free royal staycation and it happens to be fake #StPatricksDay! wrote one woman, sharing a clip panning up and down the river as a boat pumps dye into its waters.

More than 1 million people are expected to take to the streets of Chicago to take part in the Saturday celebration, including 120 parade marshals to manage crowd control.

The parade will be led byGrand Marshal Martin J. Healy Jr., a first-generation Irishman and co-founder of Healy Scanlon Law Firm of Chicago.

This article was originally published on PEOPLE.com