MLA
Shanklin, Ann. Letter from Ann Shankin (Lebanon, Kentucky) to Friends - January 31, 1863. 1863. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 20, Folder 21. https://digital.library.emory.edu/purl/112m63xtqq-cor.
APA, 6th edition
Shanklin, A. (1863). Letter from Ann Shankin (Lebanon, Kentucky) to friends - January 31, 1863 (Box 20, Folder 21) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/112m63xtqq-cor.
Chicago
Shanklin, Ann. “Letter from Ann Shankin (Lebanon, Kentucky) to Friends - January 31, 1863.” Letters (correspondence). Civil War Collection, 1863. Box 20, Folder 21. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/112m63xtqq-cor.