Belleville Telescope, Feb. 19, 1914, p. 6: "Brief Sketches of Men and Women Who Have Made Republic Co. Famous....Comrade O.O. A. Gardner, 80 years old was a privage in A. 11 Iowa Greshams Division of the 17th Corps, a fighting regiment and a fighting corps served largely in the department of Missouri."

Given his U.S. Grant connection, this had to have been very early in the war. Must have been wounded and/or motherwise discharged, and stayed behind when the regiment moved on.