While at the NARA in DC recently was a list of about 500 Confederate prisoners at Camp Chase and listed their relative with their Post Office.
Many of these Confederates would die at Camp Chase and their relative and Post Office was vital information for finding who these Confederates were according to the pre war census reports.
The Post Offices were not always the same according to the pre war census and what the Confederates had told Union authorities at Camp Chase but the distance from the two Post Offices were often within ten miles from each other.
The higher Union authorities such as Stanton had referred to the government of the South as the so-called Confederacy. The Lincoln Administration appears to have used the term the So-Called Confederacy while not officially recognizing the Confederate government.
Since the Union authorities at Camp Chase had some of the Confederates next of kin and their address when they died a letter to their loved ones could have been sent. However two postage stamps would have been required. A United States postage stamp and a stamp from the Confederate government when the letter entered Confederate territory. The latter postage stamp might have recognized the Confederacy and may have prevented the loved ones from learning of their relatives fate.
As with any war it seems the common soldier and his family paid a horrific price.
Using the 1851 United States Post Offices online has helped to confirm some the Confederates statements made to Union authorities at Camp Chase. As with any answers in research more questions arise. Which Post Office was correct? The 1860 United States census which listed a Post Office or the Confederates statements. Early indications are the Confederate statements seem to be more accurate.
Researching Post Offices during the war is a fascinating subject and some of the Post Offices would become towns and then ghost towns later on.
The statements provided by the Confederates has helped to identify some of the common given names and surnames at Camp Chase and dove tails with some of the census reports in the 1860's. Needless to say one clue leads to another and additional information such as age and family members and occupations etc emerge.