Pleasonton G. Conner is listed in Appendix D of "Earthen Walls, Iron Men: Fort DeRussy, Louisiana and the Defense of Red River" (U of Tennessee Press, 2007) as having died on July 2, 1864 of typhoid fever at St. Louis Hospital in New Orleans after being captured at Fort DeRussy. Most of the prisons in New Orleans were cotton presses, basically warehouses where cotton bales were compressed for shipment overseas or to New England cotton mills. They weren't being used much during the war, so were put to use as prisons. Conditions there were better than in most Civil War prisons, but there were still quite a few deaths from typhoid, smallpox, and various other diseases. The ladies of New Orleans did make visits to the prisons, bringing food, blankets, and other niceties, so it wasn't anything like the conditions in prisons up North. Had Conner survived, he would have been exchanged at Red River Landing on the Mississippi River on July 22 with all the other prisoners from Fort DeRussy and most of the rest of the Red River Campaign.
Is there any possibility that I could obtain a copy or a scan of the photo for the Fort DeRussy Library? Would be more than happy to pay copying fees.