MLA
Brent, E. F. Letter from E. F. Brent (Baltimore, Maryland) to [Mr. Pearce], Regarding Life in Baltimore after the War and Advising Him Not to Emigrate to South America - December 19, 1865. 1865. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 8, Folder 8. https://digital.library.emory.edu/purl/576rxwdchv-cor.
APA, 6th edition
Brent, E. F. (1865). Letter from E. F. Brent (Baltimore, Maryland) to [Mr. Pearce], regarding life in Baltimore after the war and advising him not to emigrate to South America - December 19, 1865 (Box 8, Folder 8) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/576rxwdchv-cor.
Chicago
Brent, E. F. “Letter from E. F. Brent (Baltimore, Maryland) to [Mr. Pearce], Regarding Life in Baltimore after the War and Advising Him Not to Emigrate to South America - December 19, 1865.” Letters (correspondence). Civil War Collection, 1865. Box 8, Folder 8. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/576rxwdchv-cor.