The fast-food chain founded by Dave Thomas and known for square hamburgers is Wendy's.
Dave Thomas opened the first Wendy's restaurant in Columbus, Ohio, on November 15, 1969. He named the business after his daughter Melinda Lou Thomas, whose nickname was Wendy. The chain's original name was Wendy's Old Fashioned Hamburgers.
The square patties were inspired by Kewpee Hamburgers, a Kalamazoo, Michigan, chain Thomas knew from his youth. Their corners extend beyond the bun, creating Wendy's familiar look and reflecting Thomas's belief that the burgers should appear generous rather than hidden inside the bread.
A common mix-up is confusing Wendy's with White Castle, another chain associated with distinctive-shaped burgers. McDonald's and Burger King are major competitors, but neither was founded by Dave Thomas. Wendy's later became especially associated with its Frosty dessert and the 99-cent value menu introduced in 1988.