I'm obviously late to this discussion, but I had a GGG Grandfather, John B. Huckaby, who was captured at Arkansas Post, AR on 11 Jan 1863 along with the rest of the regiment. They were sent to Camp Douglas. I wonder if he is in this group photo? Camp Douglas was a training center, a detention center for parolees, a full-fledged POW camp (beginning in Jan 1863 through the end of the war) and a point of mustering out of service at the end of the war. I'm reading Levy's book now and he mentions one of the commanders (name skips my memory at the moment) who got Union coats for the prisoners through other than normal channels.