I highly recommend you request Daniel's file from the NARA in Washington DC. If you can't visit in person, you can order online.
https://www.archives.gov/research/military/civil-war
https://www.nps.gov/civilwar/soldiers-and-sailors-database.htm
Daniel's info:
Side: Union
Location: Illinois
Battle Unit: 130th Regiment, Illinois Infantry
Function: Infantry
Alternate Name: Daniel/Callahan
If he or his widow (even a child or parent) applied for a pension, then there should be a record of it. Sometimes included are personal items such as a marriage certificate and other proof of relationship. Sometimes neighbors wrote in support of a family member applying for assistance.
I've discovered previously unknown information - date of death, place of burial, names of children who died young and never appeared in any census, children's birth dates, date and place of marriage, European birthplace. etc.
