Love Chicago-style deep-dish pizza? You have Uno’s to thank for it.

1. FOUNDER IKE SEWELL INTENDED TO OPEN A MEXICAN RESTAURANT.

Former All-American football player at University of Texas at Austin and native Texan Ike Sewell missed Mexican food when a job as a liquor salesman took him to Chicago. He partnered with World War II vet Ric Riccardo with plans to open the city’s first authentic Mexican restaurant. But when they were testing menu options, Riccardo got so sick off an enchilada he insisted they ditch the Mexican food altogether.

2. UNO’S IS THE BIRTHPLACE OF DEEP-DISH PIZZA.

Inspired by his time serving in Italy, Riccardo suggested that the pair should opt for a pizza restaurant, instead. There was already plenty of pizza in Chicago’s Little Italy neighborhood and Sewell was concerned that it wasn’t unique enough—or substantial enough. In an effort to make pizza more like the hearty enchiladas he’d anticipated, they devised a thick crust pie filled with plenty of sauce and cheese. (There is some debate about whether the two founders—who were rarely if ever seen in the kitchen—came up with the iconic dish, or if it was someone else on staff.)

3. IT WAS ORIGINALLY CALLED JUST “THE PIZZERIA.”

In 1943, Sewell and Riccardo opened their deep-dish pizza place in the basement of an old mansion on Ohio Street. At the time, it was called simply The Pizzeria and Chicagoans came mostly for the bar—that is, until free slices of deep dish quickly converted them. It was briefly known as “Riccardo’s Pizzeria,” and didn’t get “Uno” in the name until there was a “Due.”

4. THERE IS A PIZZERIA DUE.

Eventually, their deep dish became so popular that Sewell opened a second location just a few blocks away in 1955. To distinguish between the two, the original was renamed Pizzeria Uno and the offshoot was christened Pizzeria Due. In 1963, Sewell finally realized his original dream and opened Su Casa, Chicago’s first upscale Mexican restaurant.

5. SEWELL DIDN’T FRANCHISE, BUT HE DID HOLD ON TO THE ORIGINAL LOCATIONS.

For many years there were just the two: Pizzerias Uno and Due, located just a few blocks apart in Chicago. A businessman named Aaron Spencer, who owned a number of KFC locations, started asking Sewell for permission to purchase franchise rights in the mid-1970s. By 1979, Spencer had convinced Sewell to let him take the brand national. His Uno Restaurant Corporation opened locations across the country, but Sewell remained in charge of Pizzeria Uno, Pizzeria Due, and Su Casa until his death in 1990.

6. THE ORIGINAL TWO STAYED TRUE TO SEWELL’S VISION.

In 2005—long after Sewell died and his widow sold the chain—what was by then known as Uno Chicago Grill announced plans to lighten up their menu. Almost all 200 locations around the world would start offering low-calorie alternatives to the deep-dish pizza. The exceptions were those first two restaurants in Chicago. The original location of Pizzeria Uno along with Pizzeria Due were allowed to stick to tradition and continue to serve just the hearty deep-dish.

7. PIZZERIA UNO LOST FOOD WARS—BUT TO A DIRECT DESCENDANT.

Although Pizzeria Uno was the first to serve deep-dish to Chicago, it’s been long debated whether it was the best. In 2010, the Travel Channel's Food Wars decided to settle the matter once and for all by pitting Pizzeria Uno against Lou Malnati's, a Chicago-area staple since the 1970s. Unfortunately for tradition’s sake, the older Pizzeria Uno lost out to Malnati’s—but the twist is, one could not have existed without the other. Lou Malnati himself worked at Pizzeria Uno for 22 years, perfecting the Chicago deep dish, before branching out to open his own restaurant.

8. UNO’S GIVES BACK TO THE TROOPS—IN PIZZA.

Throughout December 2012, Uno’s offered coupon books for sale for $5 each. The money from the sales funded a non-profit organization, Pizzas 4 Patriots, that delivered 10,000 Uno’s pies to troops in Afghanistan for the Super Bowl. It wasn’t the first time the two organizations had partnered up. By then, they’d shipped some 50,000 pizzas to be shared by over 200,000 soldiers.

9. ALL THAT CHEESE AND BUTTERY CRUST ADDS UP.

Adds up to what? Try 1750 calories for a single serving of just a cheese and tomato deep dish. The Chicago Classic, which includes crumbled sausage in between the mozzarella cheese and chunky tomato sauce clocks in at 2300, which is considered more than a full day's worth of calories. And the sundae served deep-dish style comes in at 2700.

10. THERE'S A "FAST CASUAL" SPINOFF.

Uno Due Go is the fast casual spinoff designed for diners on the go. The menu is more general, featuring baked goods, sandwiches, salads, and even thin crust pizza. For now, the only standalone UDG—as it’s known—is located in downtown Boston, with locations in several universities and airports, as well. However, Uno Restaurant Holdings announced a plan last year to open additional locations throughout New England in the coming years.