Children's book writer Lyman Frank Baum created the popular 'Wizard of Oz' series. Ruth Plumly Thompson continued to write the series after his death.Who Was Lyman Frank Baum?Author Frank Baum had his first best-selling children's book with 1899's Father Goose, His Book. The following year, Baum scored an even bigger hit with The Wonderful Wizard of Oz and went on to write 13 more Oz books before ...