Episode 5: Enslaved Migration, Part 2

Today's episode wrapped up our bit on early enslaved migration. Many of the charts from last week are still relevant, especially the chart about the composition of immigration. Check that post out for a reminder of the data.

This post will have comparatively little to add. The South Carolina and Louisiana stories are comparatively data-poor on their own. In a future post I will have a fun chart visualizing the development of emancipation throughout the United States, but I'm gonna save that for later. And in the blog post for the next episode, I'll provide data on the growth of the enslaved population and the prominence of slavery by state.

That mean's that for today's blog post there's really not much data to present. The only chart I think is due here is a final chart showing where enslaved people arrived in the U.S., versus where they resided in 1775. So, here goes.


The above chart shows, in the red columns, the estimated number of enslaved people who arrived in each area. "Arrival" here means "disappeared from immigration record-keeping systems." It doesn't mean "ultimately resided there." As you can see, Virginia has a way bigger population compared to arrivals than most regions, while South Carolina has way more arrivals than you'd expect given the population.

There are three explanations for this. Any of this data could be wrong. The arrivals data is from a mixture of Census and Transatlantic Slave Trade Database info. They could be allocating regional disembarkations incorrectly, a note they explain in the usage guide for their data. It's possible some of those Charleston disembarkations actually disembarked in Virginia, but the boat from the Caribbean made a first stop in Charleston, and the TSTD incorrectly attributes too many disembarkations to the first port of call (Charleston) rather than a later port of call like Alexandria or Jamestown.

The second possible problem is in the enslaved population data. There was no Census in 1775. Many of the colonies held local Censuses in the 1760s and 1770s, but their methods were not all the same, and the quality of the data is not always very good. For example, in South Carolina and North Carolina specifically, official administrative and Census data from before 1775 give very widely diverging estimates depending on the exact source and year of collection. I have deferred to numbers provided in the US Census' Historical Statistics Section Z where available, but the reality is that margins of error of 10,000 or 20,000 enslaved people in the major slave-holding colonies are certainly possible. Those are big margins.

Finally, there's the explanation I noted in the Podcast itself: many enslaved people arrived in a given port, were sold to a domestic owner, cleared customs/immigration, and then were sold and moved again domestically. Intercoastal shipping of enslaved people as well as land-based trade is a documented fact. Census records show Charleston harbor exporting at least a few hundred enslaved Africans each year, mostly to more northerly colonies. Over 75 years, this could be 5,000 or 10,000 enslaved people sold away from South Carolina, towards other colonies like Virginia or New York. Likewise, enslaved people arriving in Delaware or Maryland were almost certainly sometimes sold into Virginia.

I can't give a good estimate weighting these three potential sources for error. Undoubtedly they all play some role. But exactly how much? I can't really say.

Luckily, beginning in the next episode, we're into topics where I have much more, and more reliable, data.