Ray Kroc was a salesman in the 1950s who saw potential in the Multi-Mixer Milkshake Makers being used by the McDonald brothers' small-scale restaurants. After the success of the milkshake makers, the McDonald brothers allowed Kroc to license their restaurant concept as franchises. Kroc opened a very successful franchise location in Illinois and eventually purchased the exclusive rights to the McDonald's name from the brothers in 1961. He established standard operating procedures focusing on quality, service, cleanliness and value. By emphasizing efficiency and consistency through techniques like the assembly line and strict rules regarding food holding times, Kroc grew McDonald's into the largest restaurant company in the world by the late 1960s.