John L. Sullivan was a prominent American boxer in the late 19th century, known for being the first heavyweight champion of gloved boxing. Born on October 15, 1858, in Boston, Massachusetts, he became famous for his powerful punches and charismatic personality. Sullivan's boxing career helped popularize the sport, and he was a key figure in transitioning boxing from bare-knuckle fighting to a more regulated, gloved format. Sullivan held the heavyweight title from 1882 to 1892, defending it multiple times against various challengers. His most notable fight was against James J. Corbett in 1892, which marked the end of his reign and the beginning of a new era in boxing. Sullivan's legacy continues to influence the sport today, and he is often remembered as a pioneer in professional boxing.