Barnum the musical traces Phineas Taylor Barnum`s career from 1835 to 1881 when he joined James A. Bailey to form the circus which was called The Greatest Show on Earth. Barnum is a defender of "the noble art of humbug" with a philosophy, and has a free wheeling ambition to make a fortune. He buys the oldest woman in the world, named Joyce Heath, as a sideshow attraction. Barnum builds a museum of curiosities supported by his wife Charity, who would like him to settle down.