Librarians refer to "linear feet." I donated about 13 linear feet of materials to the university Special Collections when my job was taken away and I wasn't willing to leave my work product and photo archive to others to trash or discard. It's quite a resource now.

There are serious collectors of American Civil War materials (books, etc.) You may want to do a little search on some of the items if they seem specialized or very old (I suggest BookFinder.com and eBay.)