In the late 1920s, Ross Davis ran the Hamburger Inn on Route 66 in the town of El Reno, Oklahoma. Hungry travelers headed West along the “Main Street of America” pulled over in search of good, old-fashioned American food. But as the effects of the Great Depression swept the country, beef became a luxury, and Davis had to get creative to keep his burgers affordable. He began beefing up small amounts of ground meat by smashing onions, which were still cheap, into five-cent patties. These “Depression burgers” contained about half a bulb’s worth of shredded onions, cooked into one side of the meat. At its most simple, beef, onions, and a bun completed the signature sandwich. The result was a sizzling, savory, and slightly sweet mess of crispy, sprawling onions punctuated by tender bits of ground beef.

The creation was a hit, and several other local burger joints followed suit. Confidently called a “national treasure” by multiple publications, fried onion burgers remain a niche, yet beloved, Oklahoma specialty to this day. Cooks still stretch out beef patties by filling them with onions, but cheese, pickles, and other condiments also grace today’s sandwiches. A handful of El Reno’s original eateries remain in operation, and the onion burger has also established residency 30 minutes east, in Oklahoma City. Though the original Hamburger Inn has since closed, a second location (circa 1938) is still in operation two hours south, in Ardmore, Oklahoma.