William Harrison "Jack" Dempsey (June 24, 1895 – May 31, 1983), nicknamed Kid Blackie and The Manassa Mauler, was an American professional boxer who competed from 1914 to 1927, and reigned as the world heavyweight champion from 1919 to 1926. A cultural icon of the 1920s, Dempsey's aggressive fighting style and exceptional punching power made him one of the most popular boxers in history. Many of his fights set financial and attendance records, including the first million-dollar gate. He pioneered the live broadcast of sporting events in general, and boxing matches in particular.
Dempsey is ranked tenth on The Ring magazine's list of all-time heavyweights and seventh among its Top 100 Greatest Punchers, while in 1950 the Associated Press voted him as the greatest fighter of the past 50 years. He is a member of the International Boxing Hall of Fame, and was in the previous Boxing Hall of Fame.
Born William Harrison Dempsey in Manassa, Colorado in 1895, he grew up in Colorado and West Virginia. The son of Mary Celia (née Smoot) and Hiram Dempsey, he was of part Irish ancestry and also claimed to be partially Cherokee.
William A. Dempsey, of Logan County, West Virginia, identified his son John Dempsey, Jr. of Mud Fork of Island Creek as executor of his last will and testament dated May 1, 1875. Upon payment of his debts and funeral expenses, he directed that his wife Mahulda receive the balance of his personal property while his six children receive an equal share of his real estate. His last will and testament, as witnessed by Estella, John, and Hiram Dempsey, was presented to the Logan County clerk on August 10, 1875.
Hiram and Celia Dempsey, parents to Jack, left West Virginia in 1887. One newspaper referred to them as "active workers" for the Church of Jesus Christ of Latter-day Saints.
Dempsey was baptized into the Church of Jesus Christ of Latter-day Saints, in 1903 following his eighth birthday, the "age of accountability", according to church doctrine.