The discovery of penicillin is considered a landmark in medical history, marking the beginning of antibiotic use. In 1928, Englishman Alexander Fleming discovered a strain of mold on some contaminated petri dishes: It was penicillin. It would be another decade before scientists understood the full potential of this mold. The challenge became scaling up production. American scientists lucked out when they found a strain of penicillin on a moldy cantaloupe at a Peoria, Illinois, grocery store. It grew 200 times as much as the strain Fleming found. Thanks to penicillin, the mortality rate of bacterial pneumonia fell from 18% during WWI to less than 1% in WWII.