E. Hergesheimer, Map of Virginia Showing the Distribution of its Slave Population from the Census of 1860, C. B. Graham, Lithographer (Washington, D.C.: Henry S. Graham, 1861), Library of Virginia.
The importance of slavery in the secession crisis and as a cause of the Civil War was well understood in 1861. Voters in the counties where the enslaved population was greatest elected more supporters of secession to the Virginia Convention than voters in the counties where slaves were a smaller proportion of the whole population. Lewis E. Harvie, who introduced the first secession resolution in the convention on April 4, 1861, represented Amelia and Nottoway Counties, the only two counties with more than 70 percent of their population in slavery.
This map showing the distribution of slaves in Virginia in 1860 was published in Washington, D.C., in the summer of 1861 to be "Sold for the benefit of the sick and wounded of the U.S. Army." The percentages of slaves in many of the counties are incorrect because the tabulation omitted to include the free blacks from the county totals. Captain W. R. Palmer, of the army's Department of Topographical Engineers, inscribed this copy for Secretary of the Navy Gideon Welles.