Jess Willard was one of the many boxers who had been to referred to as the "White Hope." He was thirty-seven when he met Dempsey in the ring. Six-feet-sixinches tall, and 245 pounds, he made the 195 pound Dempsey sign an agreement that he would not be held responsible if Dempsey was killed or seriously injured in the ring. The fight, promoted by George L. "Tex" Rickard, was held in Toledo, Ohio, at an outdoor arena specifically built for the title fight. In the 100 degree heat on July 4, 1919, Dempsey knocked Willard down seven times in the first round. Badly battered, Willard couldn't come out for the fourth round and Dempsey became, at twenty-four, the heavyweight champion of the world.
With his newfound fame, Dempsey became a magnet for publicity both good and bad. Kearns wanted to capitalize on the champ's instant celebrity and began signing Dempsey for everything from Vaudeville appearances to a fifteen episode serial, Daredevil Jack. Although Dempsey had planned on enjoying the fame and fortune he now had, the press came after him just as quickly. The day after his championship fight with Willard a story in the New York Tribune alleged that Dempsey was a draft dodger. He would be eventually acquitted of the charges, by the San Francisco US District Court in 1920, but the story, and the testimony of his ex-wife Cates, would plague Dempsey for nearly six years.
Dempsey's 1921 match against French war hero Georges Carpentier was called the "Battle of the Century." The fight took on international significance because of Dempsey's sullied reputation and Carpentier's as a French war hero. It was the first fight ever to be broadcast
on radio and the first to gross over one million dollars. Held at Boyle's Thirty Acres in Jersey City, the fight drew the largest crowd ever at a sporting event and forced Dempsey to defend his reputation during the short four round fight. He was given a cold reception in comparison to the loud ovation that greeted Carpentier upon entering the ring. But Dempsey's knockout of the French hero proved too much for the patriotic crowd who cheered his victory wildly.
Dempsey would successfully defend his title over the next few years, but it was his battle with the "Wild Bull of the Pampas," Argentinean Luis Firpo, that would become his next big fight. On September 14, 1923, at the Polo Grounds in New York, Dempsey took Firpo in four-and-a-half of the most intense minutes in boxing history. The crowd of 88,000, including many top celebrities like Babe Ruth and Ethel Barrymore, witnessed Dempsey knocking Firpo down seven times before Firpo landed a powerful right that threw him clear out of the ring. Landing on the press table he was thrown back in the ring by journalists and spectators only to lay Firpo out in the second. The fight's few minutes were of such ferocity that one man in the cheap seats died of heart failure.