According to "Tennesseans in the Civil War", there were two Confederate regiments identified as 55th: Browns's and McKoin's. Checking the NARA Service Records in Fold3, I did find a few files for William Autry for the year of 1862, only. Here is a summary.
William Autry
Company E
Enlisted Jan 20, 1862 at Henderson Station
Captured at Island No. 10 on April 20.
Sent to Camp Randall, Wisconsin
Paroled Aug 29/30, 1862
Sept 1862 -- Prisoner from Camp Douglas, Ill, exchanged at Vicksburg, MS.
According to the above source, it starts out the history of the 55th (Brown's) Tenn Regiment by saying:
Organized at Columbus, Kentucky February 14, 1862; reorganized September 26, 1862; field consolidation with the 46th Tennessee Infantry, January 1863; merged into 4th Consolidated Tennessee Infantry, April 1865; paroled at Greensboro, NC May 1, 1865.
Commander: Col. Alexander J. Borwn.
From details on each company:
John H. Howard, L. D. Paschal, Co. "E" Men from Henderson Station, then Madison, now Chester County, Organzied January 20, 1862.
The service records of Wm Autry matches up exactly with the records of the 55th Tennessee Regiment and Company E. Early in 1861, the Confederate army advanced into Kentucky(literally invaded it) and took over Columbus where they built a strong river fort which you can see today. They erected large siege cannons and laid a massive chain across the Mississippi River to stop Union gunboats. US General Grant's first victory was at the Battle of Belmont, Missouri, was fought on the opposite shore on Nov 7, 1861., while some Confederate regiments observed from the Kentucky side of the River. So you see the 55th Tennessee Regiment was organized at Columbus by collecting 10 Companies that had organized throughout the State of Tennessee. The men of Company E were indeed from Henderson Station & Madison County. The companies organized first in their home towns and then met at Columbus to officially organize into a Regiment.
The Confederates eventually evacuated Columbus, KY. Union forces proceeded down the Mississippi River to the next Confederate fort, Island No. 10, which included siege guns on the island on nearby river banks. The Union began the siege in March 1862. This fort was attacked with gunboats and infantry and it finally surrendered on April 8, 1862. The 55th Tennessee Regiment, except for Companies I and K were captured and taken prisoner.
I checked to see if William Autry re-enlisted into the 46 Tennessee Regiment but he wasn't on the roster. I ran a search for all Tennessee Confederate units and go no hits except the one above. I would not give up--he may have enlisted again later during the war when there was more need for men.
I ran one more search for him in the Tennessee Union regiments and got a hit. A William Autry joined the 2nd West Tennessee Cavalry Regiment--later to be re-identified as the 7th Tennessee (US) Cavalry --- on 20 Sept 1862. This date is so close to the date your William Autry was paroled from Union Prison camp.
Could this be the same man? Could he have signed a parole to not fight for the Confederacy and then agreed to fight for the US? There is a possibility because I have found many examples of soldiers deserted the Confederate cause to go fight for the Union. Many of the Union cavalry recruited men who had left Confederate units. This Union cavalryman William Autry was captured by the Confederates and sent to the notorious Andersonville Prison camp. It doesn't say he died there but there is a hand-written note that says he was paroled in 1865.
{edited to add}
However, the last record for Pvt Wm Autry of 55 Tenn Regt says his name appeared on a list of Prisoners returned to Vicksburg in Sept 1862. Whereas, this Union Tennessee cavalry regiment was organized at Union City, TN or maybe even in Kentucky.
Source: "Tennesseans in the Civil War; Part 1", published by Civil War Centennial Commission, 1964.
