This collection consists of a copybook containing about 280 letters written by Lieutenant Colonel A. P. Porter of the Union Army's Commissary of Subsistence during the American Civil War. The letters include documentation about the shipping, maintenance, and distribution of large quantities of food and supply rations among the Union Army. Along with the transport and distribution of supplies, Porter also documented inventories of many resources including cattle, livestock, and other food supplies. Many of these letters are written to other Union officers including Col. A. Beckwith and Col. H. Clarke while Lieutenant Colonel Porter was stationed at General McClellan's Headquarters.