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The story behind why Chicago dyes its river green for St. Patrick’s Day
Every March, Chicago turns its river bright green. Discover how, why, and when this iconic Chicago St. Patrick’s Day tradition takes place.
Chicago’s bright green river amidst the city’s grey landscape; It’s one of the most visually striking St. Patrick’s Day traditions in the world.
Every March, photos of this spectacle flood social media, and over 400,000 people travel to see it. Yet very few people know how or why Chicago’s river is dyed green.
If you’re thinking of checking out this iconic Chicago St. Patrick’s Day tradition, here’s what you need to know.
When does Chicago dye the river green?
Chicago’s green river is what makes this Illinois city one of the most popular US destinations to visit in March. But what many people don’t realize is that Chicago’s river only stays green for a few hours.
What’s more, the river isn’t green on St. Patrick’s Day (17 March), which is why many tourists accidentally miss out on this spectacle.
So, when does it happen?
The dyeing takes place on the Saturday before St. Patrick’s Day, when the city hosts its annual St. Patrick’s Day parade.
In 2026, this falls on Saturday, 14 March. The green river dyeing starts at 10 am, and the color typically lasts between 4 and 5 hours. The downtown St. Patrick’s Day parade follows, starting at 12 pm.
This means if you want to see the vivid green water for yourself (and get some cool Instagram shots), you’ll need to be in Chicago the morning of 14 March.
How does Chicago actually dye the river green?
If you’ve seen the photos online, you’ve surely wondered, “How on earth does the river get that color?”
A small team from the Chicago Journeymen Plumbers Union uses two motorboats to release an orange powder dye that turns green on contact with the water.
| Chicago river dyeing | Info |
|---|---|
| Who does it | Chicago Journeymen Plumbers Union |
| What is used | An orange vegetable-based powder |
| How long it takes | 45 minutes |
| How long it lasts | Typically 4–5 hours, longer if weather conditions are good |
| How much of the river is dyed | ¼ mile from Columbus Drive to State Street |
On the morning of Saturday, 14 March, you can see the team release the dye in real time and watch as the water magically transforms into an emerald wonderland.
One motorboat releases the dye into a 1/4-mile stretch of the river, while the other boat goes behind to stir it into the water. It takes around 45 minutes for the chosen part of the river to turn vivid green.
The process is free to watch, and the best viewing spots are at the Columbus Drive Bridge and the Riverwalk.
Where did the tradition come from?
This unique Chicago St. Patrick’s Day tradition dates back to 1962.
City official Stephen Bailey noticed that the plumbers’ union was using green dye to trace illegal sewage dumping. Seeing the vivid green dye on the workers’ overalls, Bailey had the idea to use it for St. Patrick’s Day.
The idea was an instant hit with residents. It quickly put Chicago’s annual parade on the map, attracting hundreds of thousands of visitors and making it one of the biggest St. Patrick’s Day celebrations in the USA.
The first time the Chicago Journeymen Plumbers Union dyed the river, they used 100 pounds of dye, and the river remained green for a week. After that, they adjusted the formula to 40 pounds to limit the color to just a few hours.
Is the dye safe for the river?
The Chicago Journeymen Plumbers Union has kept the exact formula of the dye a secret for decades, revealing only that it is a vegetable-based powder.
However, city officials and the union have repeatedly stated it is environmentally safe. There are no known lasting effects after the dye naturally fades within a few hours.
What else happens in Chicago on St. Patrick’s Day?
St. Patrick’s Day traditions are not just huge in Ireland. Many other countries celebrate St. Patrick’s Day, including the USA, and cities like Chicago host multiple festivities for this Irish holiday.
Beyond the famous river dyeing, you’ll find:
- Multiple parades: The famous Downtown St. Patrick’s Day Parade on Saturday, 14 March, kicks off at Columbus Drive. Then, the next day, there’s the South Side Irish Parade, which takes place in the Beverly/Morgan Park neighborhood.
- Street parties: In addition to the main parades, Chicago hosts numerous St. Patrick’s Day community events. For example, the Northwest Side Irish Parade takes place on Sunday, March 15 in Norwood Park. There are also festivities, including live music and dancing, at the Irish American Heritage Center and Old St. Patrick’s Church.
- Irish pub crawls: In River North and other neighborhoods across the city, you’ll find many bars hosting live music events and serving themed food and drinks. Popular spots include Guinness Open Gate Brewery, Howl At The Moon, and The Gage.
Did you know? Chicago has one of the highest concentrations of Irish ancestry in the USA and dozens of Irish pubs. As a result, the festivities are always lively, traditional, and will make you feel like you’re celebrating St. Patrick’s Day in Ireland.
Tips for visiting Chicago on St. Patrick’s Day
Whether you’re heading to Chicago from a nearby city, flying in from another state, or planning a road trip across the American Midwest, here’s how to ensure your St. Patrick’s Day is as smooth and enjoyable as can be:
- Go early: The crowds along the river build quickly, and the good spots fill up early. Therefore, it’s best to arrive at the Columbus Drive Bridge by 8 am
- Dress appropriately: March in Chicago is still very cold (2–7°C / 35–45°F), and it can be pretty rainy and windy. So wear plenty of warm layers, waterproof boots, and a waterproof jacket. And don’t forget to wear something green!
- Book accommodation months in advance: Hotels in the city center area fill up quickly for the weekend of the parade and river dyeing.
- Park outside the city: Chicago’s streets will be extremely busy, and street parking is limited. While there are some park garages where you can pre-book a spot, it may be better to park farther out and take the CTA in.
- Check out nearby cities: Chicago is one of the best weekend trips in the USA, but if you have the time, why not explore more of the Midwest? The beautiful Starved Rock State Park is just 90 minutes away, as is the Wisconsin city of Milwaukee, which has some awesome museums and breweries.
Get a travel eSIM before you go
As the streets fill up for Chicago’s St. Patrick’s Day events, the city’s public Wi-Fi will quickly become overwhelmed. Thankfully, you can avoid connection drops and spotty coverage by getting a Holafly travel eSIM ahead of your trip.
Holafly’s eSIM for the USA connects to reliable local networks, giving you fast, unlimited mobile data the moment you arrive. That means you can share those bright-green river shots, discover the best Irish pubs, and book rides across the city in the blink of an eye, no time wasted hunting for a connection.
Unlimited data. Peace of mind.
Make sure you have travel data that's there when you need it most.
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Hey, I’m Mika! I’m an SEO specialist with 7+ years of experience and a passion for travel info that actually helps you explore smarter. I write travel guides and tips backed by SEO insights so you can spend less time searching and more time adventuring.
