Jack Johnson
Jack Johnson is an iconic figure for many reasons, but mainly for his rising to prominence in the sport at a time when African-American boxers were actively kept out.
Despite being one of the top heavyweights in the world and having won the World Colored Heavyweight Championship, Johnson was not allowed to compete against heavyweight champion James J. Jeffries. The heavyweight title was off limits to black fighters.
Finally, in 1908, six years after Joe Gans had become the first African-American world champion at lightweight, Johnson fought for and won the heavyweight title. He defeated several notable ones, including Stanley Ketchel and Jeffries, who came out of retirement only to be dominated by Johnson in the Fight of the Century.