Question

Why were military prisons during the Civil War not constructed very well?

Answer 1

Probably because, they figured 'Hey we're dealing with war criminals here, they don't need a hotel'

Answer 2

Or they didn't have enough resources to make a nice prison for prisoner when they could use that money for other things.

Answer 3

Because they barely even had enough money to support the war much less for pows and another thing is there were so many troops being captured