Penicillin was discovered by Alexander Fleming in London, England in September, 1928. Fleming was a bacteriologist who worked at St. Mary's Hospital, and he found the Penicillium notatum mold on some Petri dishes containing Staphylococcus aureus upon his return from vacation.
When Alexander Fleming discovered this mold, he learned that the mold kept the staphylococci from growing normally when he viewed it under a microscope. After several weeks, Fleming grew enough mold to prove his theory that something in the Penicillium mold prevented bacterial growth and had the potential to treat infectious diseases. In March 1942, Anne Miller was the first civilian to be successfully treated with penicillin.