In my previous discussion, I posted about using the Pennsylvania Archives. I found that I could also find records on my great great great grandfather who was on the Confederate side. I was lucky that Texas has a great Confederate Pension search, and could find his pension applications, but on Footnote I was able to find other records for him which allowed me to show my grandmother where her great grandfather served in the Civil War.
Also, I find I use the Philadelphia and Washington City Directories, they are especially helpful for 1890, and the years in between census records, sometimes I can determine when a wife became a widow from the directories, or just a moment in time when she was the head of household when her husband may have been in the military when they published the directory.