If you have access to RLIN (the Research Libraries Group online database),
you can search combining subject and form/genre terms thus:
FINd SP [for subject phrase] United States History Civil War
AND [boolean operator]
FINd FG [for form/genre] diar# [truncated to find diary or diaries]
You can further limit the search by ALSo FG Mississippi
if anyone subdivided their diaries by state. If you aren't familiar with
RLIN, ask your university library's reference librarian to search for you
on RLIN.
Sue Hamburger
Manuscripts Librarian
Special Collections Dept.
W342 Pattee Library
Pennsylvania State University
University Park, PA 16802
814/865-2067
e-mail: sxh@psulias.psu.edu