MLA
Baldy, Samuel Hamilton. Letter from Samuel Hamilton Baldy (Camp Georgia, Richmond, Virginia) to His Sister, Alice, Written on Oglethorpe Light Infantry Stationary - May 31, 1861. 1861. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 1, Folder 16. https://digital.library.emory.edu/purl/791sf7m1cx-cor.
APA, 6th edition
Baldy, S. H. (1861). Letter from Samuel Hamilton Baldy (Camp Georgia, Richmond, Virginia) to his sister, Alice, written on Oglethorpe Light Infantry stationary - May 31, 1861 (Box 1, Folder 16) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/791sf7m1cx-cor.
Chicago
Baldy, Samuel Hamilton. “Letter from Samuel Hamilton Baldy (Camp Georgia, Richmond, Virginia) to His Sister, Alice, Written on Oglethorpe Light Infantry Stationary - May 31, 1861.” Letters (correspondence). Civil War Collection, 1861. Box 1, Folder 16. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/791sf7m1cx-cor.