When Leo Burnett opened an advertising agency in a small office at 360 N. Michigan Ave. on Aug. 5, 1935, he put a bowl of apples on the receptionist’s desk. He was thumbing his nose at a reporter who said it was goofy to go into advertising during the Great Depression and Burnett would soon be peddling apples on the street. The International Apple Shippers Association, faced with a surplus, had been wholesaling them to jobless men in Chicago who sold them for 5 cents each. Burnett turned apples from a sign of despair to an offer of hospitality: Welcome!...