Dempsey was born William Harrison Dempsey in Manassa, Colorado on June 24th, 1895. His family was poor and they moved around quite often so his father could find work. His parents converted to Mormonism and at the age of eight he was baptized in the Church of Latter Day Saints. Dempsey dropped out of school in elementary school to help support the family. By the age of 16 he had left home. To earn money he would go to bars and saloons to challenge people to fights. He would walk in and state "I can't sing and I can't dance, but I can lick any SOB in the house." Bets would be made and the barroom brawls ensued. There were few records kept of these events, it is said that Dempsey lost very few of these fights. Shortly after Dempsey became a professional fighter.

In Dempsey's early career he fought under various names. Because of this it is difficult to get an accurate accounting of his early fight record. It was in 1914, that Dempsey added the name "Jack" as a tribute to middleweight boxer Jack "Nonpareil" Dempsey.

 

In 1917, the United States entered World War I and Dempsey went to work in a shipyard while he continued to box. He was accused of being a slacker for not going into combat. It would be revealed later that he did enlist and was deemed 4-F.

 

In 1919, Dempsey met World Heavyweight Champion Jess Willard for a title match. Dempsey knocked Willard down in the first round. Dempsey would go on to win the fight and it created a controversy that followed him the rest of his life. There were reports after the fight that Willard had broken facial bones, ribs and a variety of other injuries too severe to have been inflicted by Dempsey's assisted hand. Accusations of Dempsey using a knuckleduster, a weapon similar to brass knuckles, in his glove. In Dempsey's case it was claimed a railroad spike was used. This theory gained some traction when in the film of the fight, something is seen lying on the canvas which is scooped up by someone in Dempsey's corner. It was brought back to live in the early 1970's when Dempsey's manager during the Willard-Dempsey fight claimed that when he wrapped Dempsey's hands he included plaster of Paris in the wrappings. This was debunked though by first hand accounts of the wrappings, the same film showing Willard inspecting Dempsey's wrappings and test performed to see what impact having plaster of Paris in the wrappings.

 

Dempsey would defend his World Heavyweight Champion title several times. One of the biggest was against Georges Carpentier, a World War I hero from France. The fight took place in New Jersey and would be the first million-dollar gate in boxing history. It would also be the first national radio broadcast. In his last successful defense of his title against Luis Ángel Firpo, the fight was broadcast to Buenos Aires.

 

During the course of Dempsey being the World Heavyweight Champion, he would become the richest athlete in the World and would be put on the cover of Time magazine.

 

In 1926, Dempsey lost his tittle to Gene Tunney. The fight had the largest attendance for a sporting event outside of racing and soccer. When he returned to his dressing room after his defeat he told his wife "Honey, I forgot to duck." Ronald Reagan would use the same line with his wife Nancy after the assassination attempt on his life.

 

Dempsey would attempt to win back his title in 1927 from Tunney. Dempsey was losing the fight until he came back and knocked Tunney to the canvas. There was a new rule instituted at the time that required the boxer to go to a neutral corner. Dempsey refused to go and the referee had to escort him over to the corner. This gave Tunney an extra 5 seconds to recover and was able to get up on the 9 count. Dempsey would later be knocked down and some say that Tunney did not go to a neutral corner and the referee counted anyway. Regardless of any controversy it would be Dempsey's last major fight. He would continue to do exhibition matches.

 

When the United States entered World War II, Dempsey enlisted again. This time in the New York National Guard. He then transferred to the United States Coast Guard Reserve. He would be honorably discharged from the Coast Guard Reserve in 1945.

 

After the war, Dempsey became a philanthropist. He notably stated that he was glad that he never had to fight Joe Louis in the ring. When Louis fell on hard times, Dempsey headed a charity for Louis to get him back on his feet.

 

Dempsey passed away on May 31st, 1983 in New York City. He said to his wife, "Don't worry honey, I'm too mean to die" just before passing away from heart failure.

 

Dempsey was a member of Kenwood Lodge #800 in Chicago, Illinois.