Not justifying Andersonville, but it was not the only case
Point Lookout Prisoner of War Camp
https://www.mycivilwar.com/pow/md-point-lookout.htmlThis camp was down the Potomac from where I grew up, but no locals were allowed to access what had not washed away of the site. It remained fenced off.
Despite the north blockading southern ports and the north having a relative bounty of supplies of all kinds, more confederate prosioners died in Northern Hands than Union Prisoners died in Confederate POW camps.
No northern camp administrators were ever tried. The Point Lookout camp, built on a sandspit with the Chesapeake Bay on one side, the Potomac River on the other, washed over during storms by brackish (undrinkable) water, in full view on a clear day of the cliffs at Westmoreland Virginia miles across the Potomac, was one of the worst.