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).