According to Bruce Catton's Grant Moves South, around the time this photo was supposedly taken, Grant had just been appointed to command at Cairo by John C. Fremont in St. Louis and arrived to find things in a deplorable shape. There were NO headquarters facilities, virtually no camps, many mosquitoes, much sickness, and a sea of mud studded with the carcasses of dead horses and mules everywhere. Grant secured probably the only decent structure in the tiny, beat-up river town which was the local Post Office and established his office on the ground floor with living quarters rooms above. He had only just been promoted brigadier general of volunteers and had yet to get time to travel to St. Louis - the nearest available location - to order a uniform, so he continued for some time to wear civilian clothes! McClernand was also a new soldier, having previously been nothing but a politician. I'm glad to see this photo because I had been thinking about it ever since reading the book, but I wonder if this really is Grant and McClernand? I can easily accept the possibility, but without knowing more about the photograph I would tend to be at least skeptical.