William Harrison Dempsey, more commonly known as Jack after age 20, was born in Manassa, Colo., on June 24, 1895, the ninth child of Hyrum and Cecilia Dempsey, both sharecroppers. The family was so poor that Jack began farming at the age of 8. From age 16 to 19 he lived in hobo jungles.

Dempsey's early boxing often took place in back rooms of frontier saloons under the name "Kid Blackie." His first fight of record was in 1915 against "One-Punch" Hancock. Dempsey's one-punch win earned him $2.50; his highest purse. Eleven years later his purse was $711,000 for his first match with Gene Tunney. Eventually called the "Manassa Mauler," Dempsey earned more than $3,500,000 in all in the ring.

Dempsey's appeal lay in his punching ability: he was a ruthless tiger stalking his prey, fast as any big cat and deadly with either paw. He won the world's heavyweight title on July 4, 1919, against Jess Willard in Toledo. With his first real punch Dempsey shattered Willard's cheekbone and knocked him down seven times in the first round. Willard was unable to answer the bell for the start of the fourth.

Two years later Dempsey drew the world's first million-dollar gate against Georges Carpentier of France, in Jersey City, NJ, scoring a fourth-round knockout. Another million-dollar bout was in 1923 against Luis Angel Firpo of Argentina; few bouts have packed such unbridled fury and spectacular savagery. Dempsey was knocked down twice, once through the ropes and out of the ring; 10 times Firpo went down, the tenth time for keeps—all within the span of 3 minutes 57 seconds. The Mauler was dethroned in Philadelphia in 1926, when Gene Tunney outpointed him before the largest crowd ever, 120,757 spectators, to witness the championship game.

Dempsey knocked out Jack Sharkey before the second Dempsey-Tunney fight a year later in Chicago