I am looking for information about my Civil War Veteran ancestor who died in 1931. I would like to see his complete record. Where can I ask for that?

I am looking for information about my Civil War Veteran Ancestor who died in 1931. His records are not at NARA. I am looking for background information that should be in there that would include his wife and where and when she died. I know when and where he died in a military veteran hospital.  thanks