Fast-food franchises have made drive-through windows as much a part of their business plan as hamburgers, fries, and shakes. Companies like McDonald’s, Burger King, Wendy’s, and dozens of others use speakers and sliding partitions to keep customers fueled on the go.

But in the case of McDonald’s, the very first drive-through wasn’t really for civilians. It was to solve a logistical problem involving members of the military.

According to AZCentral.com, the company debuted its first car-friendly window on January 24, 1975, in Sierra Vista, Arizona. While some smaller food chains had adopted the strategy, the Golden Arches considered takeout and dine-in to be its primary models.

That changed when Sierra Vista franchisee David Rich realized his location was losing a lot of business owing to a military policy. His McDonald’s was located two miles from Fort Huachuca, but members of the armed forces couldn’t grab a burger. At the time, the base's protocol mandated that the enlisted should never appear in uniform while in public.

Rich’s solution was simple. He extended a wall, inserted a window, and stationed an employee nearby to handle orders from cars that pulled up to the side of the building. That way, officers could get food while remaining in their vehicle and without violating any rules. The base’s post commander and his daughter were the first drive-through customers.

It’s worth noting that while Rich was the first to implement the window, he wasn’t the first McDonald’s operator to think of it. In 1974, an Oklahoma City, Oklahoma location got corporate approval to design and construct an elaborate drive-through with character statues—but it didn’t open until April 1975, a few months after Rich’s window.

By the end of the 1970s, over half of the company’s 5000 locations had drive-throughs. Today, it’s almost impossible to find a McDonald’s without one unless it’s in a congested urban location.

As for the pioneering Sierra Vista location: It was torn down in 1999 and rebuilt as a new McDonald’s. Pieces of the original property were auctioned, and the original drive-through partition is now on display at the Ethel H. Berger Center in town.

[h/t AZCentral.com]