MLA
Slaughter, J. H. Letter from J. H. Slaughter (Big Spring, Virginia) to "Dear Brother" - September 4, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 6, Folder 25. https://digital.library.emory.edu/purl/054kkwh7q5-cor.
APA, 6th edition
Slaughter, J. H. (1861). Letter from J. H. Slaughter (Big Spring, Virginia) to "Dear Brother" - September 4, 1861 (Box 6, Folder 25) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/054kkwh7q5-cor.
Chicago
Slaughter, J. H. “Letter from J. H. Slaughter (Big Spring, Virginia) to ‘Dear Brother’ - September 4, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 6, Folder 25. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/054kkwh7q5-cor.