I Have just read through most of these threads looking for any similar story to my ggg uncle William (Mc)Sheehy. I know there are more out there, so in case somebody is looking here someday........
William Shehea lived in Holyoke, Mass. and signed up for the 5th NY Cav. in Springfield, Mass. I spent quite a few years looking for his records because I was "stuck" on just looking within the Mass. regiments. I have since found out that Co. D consisted mostly of men from Mass. and Conn. I now have his military record and his pension file. What a motherlode! The only reason why I finally found his regiment in NY is because his name was on the Whitinsville GAR list along with his regiment. He was 19 when he signed up in 1861 as a Pvt. and he mustered out at the end of the war in 1865 as a Sgt. He was wounded twice. Shot in the face once and a sabre wound to his hip. He was a prisoner of war for what looks like just a few weeks in 1863.
I hope my story helps some others to continue their searches even outside of the State of interest. My question involves how to find out the circumstances over his short internment and are there lists of prisoners of war for the different prisons? William was at Libby Prison and neither his military file nor the pension file gives any details.
If anyone can help, thanks.

Monica