What was the condition of Civil War prison camps?

Civil War prison camps (like Andersonville in Georgia)
were generally very terrible places.  There was very poor sanitation, and rations were
generally insufficient.  Huge numbers of men who were taken prisoner died unnecessarily
in these camps.

For example, Camp Sumter, a Southern prison
camp had about 45,000 prisoners.  Of these at least 13,000 died.  At Andersonville, 29%
of all prisoners died.  This was partly because the South did not have enough resources
to properly care for the prisoners and partly because of purposeful neglect.  The North
did not do a great job taking care of its prisoners either.  For example, a prison camp
in Elmire, NY had 2,963 die of the 12,123 men who were imprisoned
there.

I suggest you take a look at the book
Don't Know Much About the Civil War, by Kenneth C. Davis.  This is
where I have found the statistics I have given here (pp. 348-54 in my
copy).