What do you think of when you think about McDonald’s? Probably the golden arches, their logo, the Big Mac, but not anything specifically Illinois-related.

McDonald’s may be the most popular restaurant chain today, but back in the early-1950s, not many people outside of California knew what it was. That changed when Ray Kroc opened the first McDonald’s franchise in Des Plaines, Illinois, on April 15, 1955.

That’s right. Today is the 71st anniversary of Illinoisans being able to enjoy McDonald’s.

Before working with McDonald’s, Kroc had quite a few different occupations. His first job was with the Red Cross Ambulance Corps during WWI, but he never went overseas. After the war ended, he became a musician and then sold paper cups. And Kroc’s last job before McDonald’s, which led to him discovering the restaurant, was as the exclusive distributor of the Multimixer, a milkshake mixing machine.

Trying to sell more Multimixers, Kroc visited the McDonald’s restaurant in California. While there, he became enthralled with how it was run. Luckily for him, he found out that the McDonald brothers, who ran the restaurant, were looking for a nationwide franchising agent. So, once again, he switched careers.

The first McDonald’s that Kroc opened was in Des Plaines, and it had over $350 of sales on its first day. Opening his first restaurant in Illinois made sense for Kroc, who grew up in Oak Park and attended Lincoln School and Oak Park River Forest High School.

After opening his first restaurant, Kroc continued to grow the McDonald’s brand, which included buying out Dick and Mac McDonald, the brothers who started the restaurant, in 1961. By the time Kroc died in 1984, there were 7,500 McDonald’s restaurants around the globe. And McDonald’s now has over 35,000 worldwide locations in more than 100 countries.

But the restaurant’s Illinois connections do not end with Kroc. McDonald’s started its Hamburger University employee training program, where employees receive Bachelor of Hamburgerology degrees, at its Elk Grove Village restaurant in 1961. And its current global headquarters is in Oak Brook, keeping its corporate leaders associated with Illinois today as well.

So the next time you pass a McDonald’s (and it is kind of hard not to), you can think about Illinois’ place in the restaurant’s history.