McDonald's Corporation acquired the exclusive rights to the McDonald's name and operating system when Ray Kroc bought out the McDonald brothers in 1961.
Ray Kroc had become the brothers' milkshake-machine distributor after visiting their unusually efficient San Bernardino restaurant. He opened a McDonald's restaurant in Des Plaines, Illinois, in 1955 and developed a large franchise network. The business relationship eventually led to Kroc obtaining control of the brand and its franchising system.
The 1961 purchase separated the expanding corporation from the original restaurant partnership. It allowed Kroc's organization to control the use of the McDonald's name, standardized procedures, restaurant appearance, and national expansion. The brothers retained their original restaurant under the name Big M for a time, but it later closed.
This event is sometimes confused with the opening of the Des Plaines restaurant. That opening was an important franchise milestone, while the buyout transferred control of the wider McDonald's brand.