Civil War soldiers and the Homestead Act
Another unusual place to find Civil War information about your ancestor at the National Archives would be Homestead records. The Homestead Act was passed during the Civil War in an effort to encourage settlement west of the Mississippi. If someone moved on to the federal land allotted to them, lived there five years, and made the necessary improvements to the land, they got that land for free. Homestead packets at the National Archives detail the whole process for each settler.
This act was also used to encourage enlistment in the Civil War, because Union Army veterans were allowed to count their time served in the war toward that five years. As this document shows, this soldier’s Homestead file had information about this Civil War service.
Homestead files are included in the federal land index here: https://glorecords.blm.gov/search/. These records are all at the National Archives, so let me know if you find your ancestor in this index. Once the National Archives reopen, I’ll be able to get the files for you!