Could not find a Major Gage from an Illinois outfit. Of course, he could have been from another state prior to moving to Chicago. Closest one I could see was a Captain Thomas Gage, Co. B, 18th Illinois Inf. Might have attained the rank of major after the war, or the rank could be honorary in GAR. The 18th was at the Siege of Vicksburg. They fortified Snyder's Bluff on 6 June and remained at that point throughout the siege.