Wilson, born in Scotland, enlisted as a Private on 9 October 1861. He was captured at the Battle of Shiloh when the men in the Hornet's Nest were compelled to surrender. Wilson wrote a letter home to his father on 17 May 1862,
"Dear Father; After being six weeks in the Southern Confederacy so called I have so much to write I scarcely know what to begin with. In the first place the most of our Regiment were taken prisoners after fighting hard all day the Battle of Pittsburg Landing.... I spent three weeks in the hospital... As soon as I was well I was removed from the hospital to the guardhouse where I staid two weeks when I, in company with 30 more prisoners from Arkansas, was started for Columbus, Mississippi.... We staid only two days at Columbus, when an order came from Beauregard to parole all the prisoners. We took an oath not to fight any more until regularly exchanged. We then started for Corinth and in due time arrived at that place. We were passed through the lines with a flag of truce and conducted to General Halleck's quarters. Here we were told that we could be exchanged in a few days and were sent to this place some five miles from the army and 8 miles from Corinth... I don't think the exchange of prisoners will take place until after the battle so I will not be in this time."
Wilson was promoted to Sergeant on 12 April 1863. He was listed as MIA at Pleasant Hill, Louisiana, but returned to his regiment on 1 July 1864. In 1942, during World War II, the State Historical Society of Iowa reprinted some of Peter Wilson's letters home in their Journal of History and Politics. http://traerstarclipper.com/page/content.detail/id/509112/Traer-Historial-Museum---The-Tediousness-of-War---Bureaucracy.html