Jack Dempsey
He won the title by beating Jess Willard on July 4, 1919. He defended the title six times before losing it to Gene Tunney in 1926. They had a rematch in 1927 and Tunney again beat Dempsey. It was during this fight where the "Long Count" took place. Dempsey knocked Tunney down in the seventh round. The referee would not start counting until Dempsey went to a neutral corner, so it is estimated that Tunney had as many as fourteen seconds to rise (instead of the usual ten).