MLA
Lewis, R. R. Letter from R. R. Lewis (Charlotte, North Carolina) to "Dear Wife" - May 6, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 4, Folder 45. https://digital.library.emory.edu/purl/665h9w0wt5-cor.
APA, 6th edition
Lewis, R. R. (1864). Letter from R. R. Lewis (Charlotte, North Carolina) to "Dear Wife" - May 6, 1864 (Box 4, Folder 45) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/665h9w0wt5-cor.
Chicago
Lewis, R. R. “Letter from R. R. Lewis (Charlotte, North Carolina) to ‘Dear Wife’ - May 6, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 4, Folder 45. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/665h9w0wt5-cor.