McDonald's opened its first restaurant under the McDonald's name in 1940.
Richard and Maurice McDonald opened the restaurant in San Bernardino, California, in 1940. It was originally a drive-in barbecue restaurant, not yet the streamlined hamburger operation that later became famous.
The brothers changed the business model in 1948, introducing a simplified menu and the Speedee Service System. That redesign created the foundation for the fast-food format associated with McDonald's branding.
Ray Kroc later expanded the company through franchising, opening a McDonald's restaurant in Des Plaines, Illinois, in 1955. The 1955 opening is therefore important, but it was not the first restaurant opened by the McDonald brothers.