The name with a middle initial is William O Smith who lived in Anderson County, TN in 1850 and 1860. So the middle initial might help - it could be that he served in the Federal, although relatives that moved to Missouri served mainly in Federal but several that served Confederate.

I see where the link you gave was to search for the regiments - any thoughts on how to search for a William O Smith within those regiments. Couldn't figure that out - and it is possible, he crossed county lines, I'm sure too.

I haven't been able to find any census records after 1860 for him. Thanks!