 1845–1892), was the daughter of Major General Napoleon J. T. Dana.General Dana, only three years older than Tidball (and six ahead of him at West Point, graduating with the USMA Class of 1842), first opposed the match, given the 20 years difference in age and life experience, but eventually consented, due to Tidball's excellent reputation and the couple's obvious affection.John and Mamie were married March 19, 1870, and built a family of their own