First, a note on reading the maps:
The maps show estimated slave migration for each county, both by net number and by rate. First, these are net numbers of forced migrants per county, that is, the number of slaves who left that county minus the number entering. Net numbers don’t reflect the total numbers of people moving back and forth. For example, if 500 people moved out of a county and 400 others moved in, the net number of out-migrants is 100.
How I came up with these numbers and mapped them:
Calculations are based on U. S. Census Bureau population schedules (ICPSR files, proofread against published volumes). For areas affected by boundary changes, I created “supercounty” blocs, summing the totals for all counties involved in each bloc and treating them as a single unit for that decade. In these cases, I had to assume rates of migration were equal across the supercounty area, with net numbers following each county’s proportion of the supercounty’s slave population.
For the war years, I used figures tallied for tax and conscription purposes by the Virginia Auditor of Public Accounts, 1861-1863. I inflated these to approximate the population as counted by the 1860 U. S. Census and to include slaves under 12 years old, who were not counted for taxation.
I used “growth-rate analysis,” a fairly simple demographic method described most clearly by Frederic Bancroft in Slave Trading in the Old South (1931), pp. 384-395, and by Michael Tadman in Speculators and Slaves: Masters, Traders, and Slaves in the Old South (1989), pp. 225-227, and “Slave Trading in the Antebellum South: An Estimate of the Extent of the Inter-Regional Slave Trade,” Journal of American Studies 13 (1974): 195-220.
First I calculated the growth rate of the entire southern slave population as the “natural” growth rate for each decade (adjusting downward in the first two decades to negate African imports). Then, for each decade, I applied that rate to the initial population of each Virginia county to find the expected “natural” population for the end of that decade, if no migration had occurred. The difference in the expected and the actual end-of-decade population (after scaling back for migrants’ post-move offspring) represents the net migration. If the actual population fell short of the expected number, the county experienced net outmigration; if the actual number was higher than the expected, there was net in-migration.
Natural growth rates for the African American population south-wide ranged roughly from 25-30% per decade. That means that slaveholders in counties showing “export” rates of 25-30% were basically selling off the natural increase for that decade (though they were actually selling off and moving young adults, mostly). Counties with rates of export of more than 25-30% experienced overall decreases in the slave population that decade.
In either case, these were remarkable demographic shifts that would be quite visible to people on the ground. Herbert Gutman put it this way: At least one-third of all African American marriages in slavery were broken up by this forced migration. An enslaved child living in the upper South in 1820 stood a 30 percent chance of being sold south by I860.
More on net numbers
Net migration figures also include “migration” out of the slave population by several means: flight, manumission, sale, and migration with moving planters. Flight and manumission, important as they were to the individuals involved, altered overall patterns only slightly, except perhaps in western Virginia, where small changes in numbers could change rates substantially and where even net numbers were sometimes significant. Net numbers may also hide illegal slave “imports,” although by the time of the Revolution, few were likely to have been smuggled into the Chesapeake, according to Alan Kulikoff (“Uprooted Peoples,” in Berlin and Hoffman, eds., Slavery and Freedom), due to the general labor glut there.
The proportion of enslaved African Americans who were sold off and taken south by slave traders vs. those relocated by planters was once subject of debate, with the assumption that planter migrations carried entire communities intact. Michael Tadman (Speculators and Slaves, 1989) successfully discredited the low (17%) estimate of trader-migration forwarded by Robert Fogel and Stanley Engerman in Time on the Cross (1974); Tadman’s estimate ranges from 60% to 80% of the total migration. We now know that this trader/planter dichotomy itself is somewhat false, as planters broke up many families as well, often taking south only the most fit to clear fields, establish crops, and start bearing children.
And of course, planters were the ones selling to slave traders in the first place. All these migrations, then, were forced migrations driven by the slave market. The slave market and slavery were one and the same.
Copyright 2017 © Phillip Troutman. Unmodified not-for-profit usage is freely granted with acknowledgement. Cite as: Phillip Troutman,Virginia’s Slave Trade blog, virginiaslavetrade.wordpress.com (your access date).