Much thanks for the information. It follows that Bonsall was in the 2nd Ohio only a short time. I take it he was not in the regiment at the time it was reorganized into the 2nd Ohio Volunteers? What about his service with the Engineer Brigade of the Army of the Ohio? I know that Bonsall took pictures of maps and terrain features while working for Rosecrans. There are records of passes given by the adjutant of the 2nd Regiment (unkown state) granting him permission to travel to various locations to take pictures. The same applies to passes given from Rosecrans Headquarters.

I am attempting to time line this mans service history as well as fill in the blank spots between his picture taking before, during and after Chickamauga along with his famous pictures taken during the Chattanooga campaign.