Hergesheimer, E. (Edwin),  Leonhardt, Theo. (Theodore),  Graham, H. S. (Henry S.),  United States Coast Survey,  and United States. Bureau of the Census. .  "Map showing the distribution of the slave population of the southern states of the United States."  Map.  1861.  Norman B. Leventhal Map & Education Center,  https://collections.leventhalmap.org/search/commonwealth:w9505r836 (accessed February 18, 2019).