From Lincoln Mullen's blog entry, "Mapping the Spread of American Slavery" -- and another version at the Smithsonian site:
|This one was a favorite of President Lincoln's.|
"The map showed at a glance the large-scale patterns of slavery in the American South: the concentrations of slavery in eastern Virginia, in South Carolina, and most of all along the Mississippi. It also repaid closer examination, since each county was labeled with the exact percentage enslaved. The map of slavery was one of many thematic maps produced in the nineteenth century United States.
This is part of Mullen's commentary as to the utility of such maps to doing history and creating one's arguments:
The first thing to observe is that slavery spread more than it grew. The population of slaves in 1790 or 1800 was already very high compared the maximum population levels. In fact, in Charleston County, South Carolina (one of the counties with the highest populations of slaves) the number of enslaved people in 1860 was only 63% of what it had been in 1840. This is not to say that the total number of slaves in the eastern seaboard states did not go up over time. But the number of enslaved people in a particular place did not grow at anything like the rate of free people in the north. The free population in the north both grew in the same place and spread to the west. The slave population had a different dynamic. It grew in intensity in places around the Chesapeake bay, even as slavery was gradually abolished in the North. But primarily the slave population spread to the fertile crescent of lands in Georgia, Alabama, and Mississippi, and most of all to the Mississippi River valley. Below you can see two animations of the density of the slave population and the density of the total population (keep in mind that the scales are different). What you see in these maps is the spread of slavery through the domestic slave trade. You also see the origins of the sectional crisis in the continual expansion of slavery.
I.e. we see the domestic slave breeding industry and the domestic slave trade in action in his animated maps.
These maps, and their use for understanding populations' numbers, growth and distribution, demonstrate how important statistics are to understanding history, particularly within the context of both past and present. A person cannot understand or "do" history without numbers, starting, of course, with the first law of history: chronology.