Here are some links. You may also want to try some of these sources mentioned. I have read that some of Ken Burns ideas hare a bit slanted I would suggest you do the legwork and get a more unbiased view.

http://www.civilwarhistory.com/ElmiraPrison/Elmira.htm

http://www.angelfire.com/ny5/elmiraprison/body.html

http://www.cityofelmira.net/history/prison_camp.html

http://www.civilwaralbum.com/misc12/elmira1.htm

http://www.chemunghistory.com/prisoncamp.html

http://www.joycetice.com/military/prison.htm

http://www.novelguide.com/a/discover/dah_03/dah_03_01352.html

HTH

GP