MLA
Smith, T. S. Letter from T. S. Smith (Treasury Department, First Auditor's Office [Washington]), to John Shulock (Savannah, Georgia) - November 15, 1869. 1869. Stuart A. Rose Manuscript, Archives, and Rare Book Library, Box 20, Folder 25. https://digital.library.emory.edu/purl/368kd51db5-cor.
APA, 6th edition
Smith, T. S. (1869). Letter from T. S. Smith (Treasury Department, First Auditor's Office [Washington]), to John Shulock (Savannah, Georgia) - November 15, 1869 (Box 20, Folder 25) [Letters (correspondence)]. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/368kd51db5-cor.
Chicago
Smith, T. S. “Letter from T. S. Smith (Treasury Department, First Auditor's Office [Washington]), to John Shulock (Savannah, Georgia) - November 15, 1869.” Letters (correspondence). Civil War Collection, 1869. Box 20, Folder 25. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/368kd51db5-cor.