Alan,
What I found interesting was that at the battle of Belmont in 1861 in Missouri was the fact that Illinois men were on both sides. Captain Cunningham was an officer in company G or the Tenn. 15th and on the other side was his brother in law, Col. John "BlackJack" Logan who was married to Cunninghams sister Mary. Logan commanded the 31st Illinois at that time. In May of 63, Cunningham to a leave and went north and by that fall he had a commision in the Union army with the rank of Captain and he became Logans aide who by then was a major general.
Later, Logan was a high mucky muck in the GAR and is credited with the creating the Norths Decoration day.
FC