That's an interesting question that I haven't thought about. There is a book called "Portals to Hell" (don't remember the author). It tells about the yankee prisons and is as far as I know one of the very few that even mentions Hart's Island. The prison was only used at the very end of the war. My gr gr grandfather was captured in Petersburg around the 1st of April 1865 right at the end of the war. He was held until June 9 when he and the others were mustered out.

I have some information I could send you that I felt was relevant to the soldiers at Hart's Island. I couldn't find much. But if you have an email I could send the 2 .jpg pages I have.