Mapping Slavery. In September 1861 Edwin Hergesheimer of the United States Coast Survey produced a map based on data from the 1860 census showing the distribution of slaves across the South. It's interesting to compare this to other maps. Map of secession votes by counties throughout the South (with the color scale reversed) and for secession in Virginia. Areas with fewer slaves were less likely to vote for secession.
The Coast Survey map is pictured in Francis Bicknell Carpenter's paintingFirst Reading of the Emancipation Proclamation of President Lincoln. The president used the map to identify possible areas of Southern Unionists and follow the advance of Union troops. The map on the table behind Secretary of State William Seward is the Coast Survey's 1863 "Map of the State of Virginia."