Rocky Marciano retires at 49-0
A relative latecomer to the sport, Rocky Marciano started boxing while in the service during WWII. His amateur career was solid -- an 8-4 record. But once he turned pro, he never lost again. Along the way, the Brockton Blockbuster beat Joe Louis and earned the heavyweight title with a 13th-round knockout of Jersey Joe Walcott. Marciano was only 32 when he retired.