City Secrets is a new mental_floss feature sharing fascinating facts and stories from the histories of famous cities.

The City of Big Shoulders, The Windy City, City on the Make—no matter what you call it, Chicago has plenty of stories (and secrets) to tell. Here's but a small selection. 

1. O'HARE AIRPORT IS NAMED AFTER THE HEROIC SON OF AL CAPONE'S LAWYER.

Chicago’s airport—which by some counts is the busiest in the world—was originally named Orchard Field. In 1949, at the suggestion of Chicago publishing baron Robert R. McCormick, it was renamed O’Hare Airport to honor Edward “Butch” O’Hare, a Navy fighter pilot and Medal of Honor recipient who perished in World War II.

While Butch O’Hare’s heroism is well-documented, his father’s story is noteworthy as well. Edward J. O’Hare, a.k.a. “Easy Eddie,” was a lawyer, dog track owner, and business associate of Al Capone, often operating as counsel for the notorious crime boss. The two got along swimmingly until Capone was charged with tax evasion in 1931—charges that sprouted from O’Hare’s cooperation with the government.

In 1939, shortly before Capone was paroled and released from Alcatraz, “Easy Eddie” O’Hare was shot to death in his car by two men at the intersection of Ogden Avenue and Rockwell Street. While no one knows for sure whether or not the hit was ordered by Capone, the murder had all the markings of a gangland assassination.

2. THE CHICAGO FIRE WAS BOUND TO HAPPEN.

Mrs. O’Leary and her cow get a bad rap. First of all, the cow is likely innocent; its supposed culpability for the Great Chicago Fire of 1871 is nothing more than the result of unsubstantiated rumor and bovine slander. Secondly, the city would’ve burned down sooner or later, as it was a tinder box waiting for the slightest spark. As DePaul University professor Joseph P. Schwieterman told WBEZ, “Fires would have been inevitable.”

The city was densely packed with wooden homes, buildings, and over 561 miles of wood sidewalks. After the fire, wood construction was banned in downtown Chicago, a move that stymied Chicago’s other big fire—a blaze started on the city’s southside in 1874 that killed 20 people and destroyed about 47 acres—before it could match or exceed 1871’s disaster. So, had the Great Chicago Fire not happened in 1871, there would likely have only been a 3-year wait for a similar occurrence. 

3. THERE'S A SECRET CHICAGO SYMBOL ALL OVER THE CITY—YOU JUST NEED TO KNOW WHAT TO LOOK FOR.

Flickr User Daniel X. O'Neil // CC BY 2.0

Chicagoans love their flag and they aren’t afraid to show it. (Chances are, you know someone who knows someone who knows someone who has a Chicago flag tattoo.) The four red stars and two blue stripes are unmistakable, but the city has another ubiquitous symbol—though it remains unnoticed by most Chicagoans as they go about their daily business.

It’s called an “official municipal device,” and it was created in 1892. Its appearance is defined in the city code, which states, “The municipal device, for use by the varied unofficial interests of the city and its people, shall show a Y-shaped figure in a circle, colored and designed to suit individual tastes and needs.”

The symbol represents where the three branches of the Chicago River meet, and it can be spotted everywhere from the flashy marquee of the Chicago Theater to lamp posts, traffic control boxes, manhole covers, libraries, and more.

Now that you know what it looks like, you won’t be able to miss it.

4. THE CHICAGO RIVER WON A MASSIVE COURT CASE ...

Flickr User Daniel X. O'Neil // CC BY 2.0

As Chicago grew in the late 19th century, so did its pollution. Waste from factories and citizens flowed down the Chicago River into Lake Michigan—the city’s water source—and became a public health hazard. Chicago responded by doing the seemingly impossible: In 1900, engineers from the Sanitary District of Chicago reversed the flow of the river. Problem solved … for Chicago.

At the other end of the river’s path sits St. Louis, and all that waste and pollution from Chicagoans flowed down into the source of that city's drinking water, the Mississippi River. Missouri sued Illinois and, because it was a dispute between states, the case was heard by the Supreme Court. The highest court in the land ruled in Illinois’ favor in 1906, deciding that Missouri couldn’t prove the sewage was necessarily Chicago’s and that the river didn't seem any different from before.

5. ... THE RIVER LOST A BIG LAWSUIT, TOO.

Flickr User Antonio Bovino // CC BY 2.0

Fast-forward to the 1920s: Chicago was drawing so much water from Lake Michigan to flush its sewage, water levels in all the Great Lakes (except for Lake Superior) started to noticeably recede. The effects were so dramatic, harbors in states as far away as New York reported diminished shipping capabilities. These states sued and a prolonged and complicated court case resulted in Chicago having to build its own sewage treatment plants.

Funnily enough, the state that was on Illinois’ side during this battle? Their old foe Missouri, who had taken a liking to their ports' increased water heights courtesy of the reversed Chicago River.

6. THERE'S A TUNNEL SYSTEM DOWNTOWN TO SHIELD CHICAGOANS FROM THE WEATHER.

Flickr User John Greenfield // CC BY 2.0

The Chicago Pedway allows pedestrians to travel through a large section of the Loop without having to face the winter cold (or summer heat, or spring showers, or fall … pleasantness). The tunnels, bridges, and concourses that make up the Pedway feature shops, restaurants, and access to train systems.

Construction on the Pedway began in 1951, and it’s getting bigger all the time [PDF]. Currently, it connects an area longer than 40 blocks, and some accessible highlights include City Hall, the Chicago Cultural Center, and Millennium Park. And, because it’s Chicago, you can go on a guided architecture tour inside the Pedway.

7. PEOPLE WHO SHOVEL THEIR SIDEWALKS WELL ARE ELIGIBLE FOR AN AWARD FROM THE CITY.

As anyone who has cleared a parking space and called “dibs” on it with a lawn chair and three-legged Weber grill will tell you, shoveling is a big deal in Chicago. To wit, the city has an official prize for shoveling excellence: The “Winter Wonder” Award.

Winners get a shoutout on the Chicago Department of Transportation website and receive an “award signed by the co-chairs of MPAC”—that’s the Mayor's Pedestrian Advisory Council, natch.

8. ACCESS TO THE CITY'S BEST SKYSCRAPER OBSERVATION DECKS COSTS YOU ONLY A DRINK OR DINNER.

Flickr User TheeErin // CC BY-SA 2.0

Sure, it may not be a cheap drink or dinner, but it's a far more relaxed way to take in the skyline. To name a few, the John Hancock's Signature Room at the 95th, Lake Point Tower's Cité, and (if you're willing to become a member) the Aon Center's Mid-America Club all offer incredible views to go along with your meal.

Lake Point Tower's view is especially rare. The building—which was, for a time, the tallest apartment building in the world—is the only building in Chicago that sits east of Lake Shore Drive. When it was built in the mid-60s, it was one of three. The change happened in 1987, when a section of Lake Shore Drive was rerouted to remove dangerously sharp turns, and the new path took it east of the other two buildings—but not Lake Point Tower, making it a Chicago anomaly.

9. THE BEAUTIFUL LAKEFRONT IS THANKS TO A CRANKY AND LITIGIOUS CATALOG BARON.

Flickr User dtadd // CC BY-SA 2.0

If you've ever taken a jog on one of Chicago's lakefront paths or relaxed on one of the city's beaches, you have Aaron Montgomery Ward to thank. After making a fortune with his mail-order catalog business, Ward spent his twilight years suing into oblivion anyone who dared to try to build private property on the lakefront.

Citing Daniel Burnham's original Plan for Chicago, which states that the lakefront was to be "Public Ground—A Common to Remain Forever Open, Clear, and Free of Any Buildings, or Other Obstruction," Ward spent a considerable part of his fortune making sure Burnham's words were honored, dragging anyone who tried to build private property on the lake to court. In 1909, the Supreme Court of Illinois backed Ward, and city's lakefront has remained public to this day. After the ruling, he remarked:

I think there is not another man in Chicago who would have spent the money I have spent in this fight with the certainty that even gratitude would be denied as interest. I fought for the poor people of Chicago, not the millionaires ... Perhaps I may yet see the public appreciate my efforts.

If only all lawsuits reaped such reward.