MLA
Drayton, Thomas F. Letter from Thomas F. Drayton (Charleston, South Carolina) to David Flavel Jamison, about a plan for firing upon Fort Sumter - January 10, 1861. January 10, 1861. Civil War Collection. Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/204rjdfp3b-cor.
APA, 6th edition
Drayton, Thomas F. (January 10, 1861)[Letter from Thomas F. Drayton (Charleston, South Carolina) to David Flavel Jamison, about a plan for firing upon Fort Sumter - January 10, 1861]. Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/204rjdfp3b-cor.
Chicago
Drayton, Thomas F, Letter from Thomas F. Drayton (Charleston, South Carolina) to David Flavel Jamison, about a plan for firing upon Fort Sumter - January 10, 1861, January 10, 1861, Civil War Collection, Stuart A. Rose Manuscript, Archives, and Rare Book Library. https://digital.library.emory.edu/purl/204rjdfp3b-cor.