I am looking for information on my GGGrandfathers unit. He served with the 15th Texas Cavalry Company H and was captured along with the rest of the 15th at Arkansas Post January 11 1863 and sent to Camp Douglas Il. However when his unit was exchanged later that spring he was left behind at Camp Douglas. His records state that he was left sick in the Hospital. He stayed at Camp Douglas until March 1865
He was exchanged in late March 1865 at Boulware's Wharf on the James River VA and rec'd at City Point VA by the 21st of March. He was again captured at Bruinsburg Miss. April 23 1865 and sent to Alton Prison where he was paroled June 19 1865.
My queston is: What unit would he have been with in March/April 1865? The 15th Texas Cavalry doesn't seem to have been in that area at that time. Is there away to find out which prisoners were exchanged at that time and what units they were sent to? What units were active in Miss. or VA at those times?