P.T. Barnum
Name at birth: Phineas Taylor Barnum
P.T. Barnum bought the American Museum in New York City in 1841 and turned it into an exhibition hall for the presentation of "freaks" such as "The Feejee Mermaid" and the ultra-diminuitive General Tom Thumb (real name: Charles Stratton). A brilliant and shameless promoter, Barnum weathered accusations of fraud with the attitude that there was no such thing as bad press, and he became one of the richest men in America. His string of successful acts included European opera singer Jenny Lind, Jumbo the elephant and conjoined twins Chang and Eng Bunker. In 1871 Barnum opened a circus, billed as "The Greatest Show On Earth." In 1881 he merged with competitor James Bailey, forming Barnum & Bailey's Circus (eventually it became today's Ringling Bros. and Barnum & Bailey Circus).
Extra credit: Although it's unclear if he ever said it, Barnum is frequently cited as the source of the quote: "There's a sucker born every minute."
Blog posts mentioning P.T. Barnum:
Evel Knievel, "Bone-Shattering" Stuntman