Heydler was a government printer in Washington in the 1880s. His interest in baseball led him into umpiring and later sportswriting. He became secretary to NL president Harry Pulliam and became interim president after Pulliam’s suicide. He became secretary-treasurer under president John K. Tener, and succeeded Tener as NL president in 1918. Heydler was not very energetic in investigating scandal or in opposing league owners, but he was innovative in his thinking. He supported the selection of Judge Kenesaw Landis as Commissioner of Baseball in 1920, helped establish the Baseball Hall of Fame, and proposed the designated hitter as early as 1929. After resigning as president in 1934, he served as NL chairman of the board until his death.