Boxer Jack Dempsey heralded the Golden Age of Sports. Like Babe Ruth, Red Grange, Bill Tilden, and Bobby Jones, Dempsey was the face of his sport. "In the ring, he was a tiger without mercy who shuffled forward in a bobbing crouch, humming a barely audible tune and punching to the rhythm of the song," wrote Red Smith in the Washington Post, adding, "he was 187 pounds of unbridled violence." Jack Dempsey was a box-office magnet, attracting not only the first $1 million but also the first $2 million gate. He held the world heavyweight boxing title from July 4, 1919, when he knocked out Jesse Willard—who retired at the end of the third round with a broken jaw, two broken ribs, and four teeth missing—until September 23, 1926, when he lost it to Gene "The Fighting Marine" Tunney on points after ten rounds. Of a total of 80 recorded...