MLA
Speir, James H. Letter by James H. Speir (Pike County, Georgia) to "Dear Mother and Sister" - September 25, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 53. https://digital.library.emory.edu/purl/1848pk0pqm-cor.
APA, 6th edition
Speir, J. H. (1864). Letter by James H. Speir (Pike County, Georgia) to "Dear Mother and Sister" - September 25, 1864 (Box 6, Folder 53) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/1848pk0pqm-cor.
Chicago
Speir, James H. “Letter by James H. Speir (Pike County, Georgia) to ‘Dear Mother and Sister’ - September 25, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 6, Folder 53. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/1848pk0pqm-cor.