America's number one pharmacy came into being in 1901 as a diminutive neighbourhood drugstore measuring just 50 feet by 20 feet. The pharmacy, located on the corner of Bowen and Cottage Grove Avenues in Chicago, was opened by Charles R Walgreen, who launched 19 stores by 1920. Interestingly, the chain owes much of its early success to prohibition during the 1920s. It made a killing selling prescription whiskey, which was legal at the time.