MLA
Bancroft, George. Letter from George Bancroft (Medical Purveyor's Office, Columbia, South Carolina) to "Dear Charley" - August 5, 1864. 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 17. https://digital.library.emory.edu/purl/044bnzs8jb-cor.
APA, 6th edition
Bancroft, G. (1864). Letter from George Bancroft (Medical Purveyor's Office, Columbia, South Carolina) to "Dear Charley" - August 5, 1864 (Box 1, Folder 17) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/044bnzs8jb-cor.
Chicago
Bancroft, George. “Letter from George Bancroft (Medical Purveyor's Office, Columbia, South Carolina) to ‘Dear Charley’ - August 5, 1864.” Letters (correspondence). Civil War Collection, 1864. Box 1, Folder 17. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/044bnzs8jb-cor.