Hello Jeanie:
The Louisville Military Prison was a transit station for Confederate POWs being shipped north from the Atlanta Campaign in the summer of 1864. The National Park Service's online Index to the CMSR shows a Corporal (not Colonel) George N. MITCHELL enrolled in the 1st Florida Infantry. Corporal Mitchell would have passed through the Louisville Military Prison en route to the Rock Island POW Camp in Illinois.
The 1st Florida Infantry regiment was consolidated with the 3rd Florida Infantry in December 1862, according to Crute’s unit history posted on the NPS website. From other sources, I found that the consolidated 1st/3rd Florida Infantry served in Finley’s Brigade in the Confederate Army of Tennessee.
In February and March 1865, a general exchange of sick and disabled prisoners was agreed to and the delivery of POWs took place at Boulware’s Wharf on the James River a few miles east of Richmond. POWs from Rock Island included in this early release would have been shipped across country to either Fort Delaware or Point Lookout and then delivered to Confederate authorites on the James River. Corporal George N. MITCHELL's name does not appear in the Fort Delaware Society database.
Immediately following delivery to their own side, the returning Confederates were examined in Richmond hospitals, treated as necessary, and released. If deemed fit for duty, they were declared exchanged and returned to their units. However, most were not fit for duty and were released on 60 day furloughs as paroled prisoners of war. What remained of the Florida units of Finley’s Brigade was surrendered at Greensboro, North Carolina on April 26, 1865 under the agreement between Generals Sherman and Johnston.
The details of all of this as it pertains to an individual soldier should appear in that soldier’s Compiled Military Service Records which come from the National Archives. They have an excellent webpage explaining what these records are and how to order them online. See http://www.archives.gov/genealogy/military/civil-war/index.html#confed
You can also purchase copies of these same records through the Military Records Research Service which supports these Civil War Message Boards at http://history-sites.com/research/index.html [see linkage at the top of this page]. Purchasing copies of the CMSR and other records through MRRS gives financial support to the History-Sites.com CWMBs which provides a place to exchange Civil War research information at no cost to the participants.
I hope all of this is of some help and I urge you to get a copy of your ancestor’s Compiled Military Service Records.
Hugh Simmons
Fort Delaware Society
http://www.del.net/org/fort