Jack Dempsey (1895 – 1983), professional boxer, dies at age 87. Jack Dempsey, also known as "The Manassa Mauler," had an incredible career as one of the world's most successful and iconic professional boxers. Born in Manassa, Colorado in 1895, Dempsey's boxing career spanned two decades, from 1914 to 1927. Dempsey held the world heavyweight championship title from 1919 to 1926 and is considered one of the greatest heavyweight champions of all time. He went on to become an actor and public speaker after he retired from professional boxing. After battling bone cancer for nearly three years, Dempsey died at age 87 on May 31, 1983. He left behind a legacy as an iconic natural athlete, known around the world for his boxing prowess. Dempsey will be remembered particularly for his dedication to the sport of boxing, which he is credited with bringing tremendous recognition and excitement to.