I don't know about the Federal Army, but they may have had a criminal prison in or near New Orleans. On the other hand the Confederate Army in Louisiana was never in one place long enough to maintain any type of permanent prison. Walker's Texas Division in Louisiana had a Court Martial Commission made up of 5 or 6 officers that took action fairly quickly. A major crime like desertion or murder could bring the death Sentence and it was carried out by a squad of 24 executioners, twelve loaded with blank cartridges and twelve loaded with shot cartridges. For a crime like stealing a hog the guilty could be "drumed out of camp" and sent home in disgrace. In others cases it could be just a reduction of rank. Lt. S.T. Rister of the 17 Texas got in an argument with another officer over crossing a Bayou to cross the Mississippi River to the east. The crossing was never made and Rister was to be charged with insighting something like a riot. By the time the charge got passed around and on to General Polignac the charge was dropped or just forgot about. After the Battle of Milliken's Bend of June 6-8, 1863 and the threat of crossing the Mississippi River to the east in 1864, this brought on a large backup of cases for desertion on the Court Martial Commission. I believe these prisioners were just keep with the Army near Alexandria and or Sheveport until their trials. Some of these found guilty may have been sent along with other prisoners to a prison in east Texas. These are my thoughts on the matter, maybe someone else has more information on formal military prisons in Louisiana.