MLA
Godwin, Neil. Letter from Niel Godwin (Camp near Palmetta, Georgia) to Molly Keahey. Niel Godwin Was a Lieutenant in the 33rd Alabama Infantry Regiment - September 24, 1864 (Typescript). 1864. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 4, Folder 24. https://digital.library.emory.edu/purl/245q83bm2p-cor.
APA, 6th edition
Godwin, N. (1864). Letter from Niel Godwin (Camp near Palmetta, Georgia) to Molly Keahey. Niel Godwin was a lieutenant in the 33rd Alabama Infantry Regiment - September 24, 1864 (typescript) (Box 4, Folder 24) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/245q83bm2p-cor.
Chicago
Godwin, Neil. “Letter from Niel Godwin (Camp near Palmetta, Georgia) to Molly Keahey. Niel Godwin Was a Lieutenant in the 33rd Alabama Infantry Regiment - September 24, 1864 (Typescript).” Letters (correspondence). Civil War Collection, 1864. Box 4, Folder 24. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/245q83bm2p-cor.