Ron,
Try what Ann suggests. Go to www.ilsos.gov/genealogy/CivilWarController
Just as I typed it and Fill out the form with as much info as you have and you will have a chance to obtain a Illinois Civil War Detail Report. It will tell you his name, rank, company, unit, residence, age at enlistment, height, hair color, eye color, complexion, marital status and occupation at the time of enlistment. When he joined, where he joined, who swore him in, how long the enlistment was for, etc. Lots of info .
Frank