Joe Dempsey was one of three famous rowing brothers and, in fact, the 1904 Vesper eight was coached by his oldest brother, Jim. Both Joe and Jim Dempsey began rowing with the Penn Barge Club, but later switched to Vesper. In 1905 Dempsey joined the Vesper Crew at the Henley Royal Regatta, but Vesper was defeated by ¾-of-a-boat length by Leander Club, a renowned British eight that was not present at St. Louis in 1904. Dempsey later became Jack Kelly’s first coach.
In Golden Book of Olympic Games the dates are erraneousy given as 27 SEP 1872 - 9 OCT 1930. Those dates belong actually to his older brother Jim, who also coached the 1904 Vesper eight crew.