James Jackson Jeffries ("The Boilermaker") (born April 15, 1875 in Carroll, Ohio, United States – died March 3, 1953 in Burbank, California) was a world heavyweight boxing champion.

Jeffries stood 6 ft 3 in tall and weighed 225 in his prime. Despite his bulk, Jeffries, who was not a trained sprinter, could run the 100 yards in a little more than ten seconds. The world record in 1900 for the 100 yard dash was a little under ten seconds. While working as a sparring partner for James J. Corbett, Jeffries consistently outsprinted Corbett. Corbett was an outstanding all around athlete and had never lost a footrace to any of his campmates. Jeffries was also nimble and could purportedly high jump over six feet.

His greatest assets were his enormous strength and stamina. Using a technique taught to him by his trainer, former middleweight champion Tommy Ryan, Jeffries fought out of a crouch with his left arm extended forward. He was able to absorb tremendous punishment while wearing his opponents down. A natural left-hander, he possessed one punch knockout power in his left hook.
Source : Wikipedia