Originally called Insta-Burger King, the company was founded in Florida in 1953 by Keith Kramer and Matthew Burns. Their Insta-Broiler oven was so successful at cooking hamburgers that they required all of their franchised restaurants to use the oven. After the chain ran into financial difficulties, it was purchased by its Miami-based franchisees, James McLamore and David Edgerton, in 1955. The new owners renamed the company Burger King, and the restaurant chain introduced the first Whopper sandwich in 1957. Expanding to over 250 locations in the United States, the company was sold in 1967 to Pillsbury Corporation.