MLA
Raintree, J. M. Letter from J. M. Raintree (Portsmouth, Virginia) to "Dear Thom" - June 14, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 5, Folder 55. https://digital.library.emory.edu/purl/525k98sg8s-cor.
APA, 6th edition
Raintree, J. M. (1861). Letter from J. M. Raintree (Portsmouth, Virginia) to "Dear Thom" - June 14, 1861 (Box 5, Folder 55) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/525k98sg8s-cor.
Chicago
Raintree, J. M. “Letter from J. M. Raintree (Portsmouth, Virginia) to ‘Dear Thom’ - June 14, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 5, Folder 55. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/525k98sg8s-cor.