The McDonald brothers' first passion was barbecue, so much so that they opened a barbecue stand in California in the late 1930s. Sure, it sold hamburgers (and hot dogs) too, but that was not the San Bernardino stand's main staple. When the economy dictated that the self-service establishment reduce and specialize its menu, that's when the fast-food hamburger, fries and shake idea was born.
It wasn't until Ray Kroc arrived to sell the brothers 48 mixers for making their shakes that Kroc and the McDonalds brothers met -- and hit it off, at first. Kroc had significantly more business savvy and vision than the brothers, who hadn't really thought about expansion. Kroc convinced the brothers to let him open a franchise in Illinois. He came up with so many innovative ideas to advance the business that he established a McDonald's Corporation, sold additional franchises and then persuaded the McDonalds to sell him rights to the entire business. The success of McDonald's under the leadership of Kroc is actually known in fast food circles as "the Kroc influence."
Although the brothers got $2.7 million from Kroc for selling their creation, they reportedly were not happy about it. They reportedly maintained a rather hostile relationship with Kroc. According to various versions of history, the brothers had an oral contract to retain a percentage of the business but Kroc refused to honor the agreement. Also, Kroc reportedly forced the closure of the McDonald's original San Bernardino eatery by opening a new, expansive McDonalds across the road.