True story about Jack Dempsey, one of the most famous professional US boxers who made his name in the 1920's as the world heavyweight champion and media sensation.True story about Jack Dempsey, one of the most famous professional US boxers who made his name in the 1920's as the world heavyweight champion and media sensation.True story about Jack Dempsey, one of the most famous professional US boxers who made his name in the 1920's as the world heavyweight champion and media sensation.