The demographics of American slavery according to new research by Eric Foner, Lincoln Mullen, and more.

Ten Surprising Facts About the Demographics of American Slavery

Ten Surprising Facts About the Demographics of American Slavery

Our defining institution, in nine lives.
June 12 2015 12:07 PM

The Surprising Demographics of American Slavery

New research and new resources are changing our view of how slavery worked in early America.

Manifest for the schooner LaFayette. (Click to see the full manifest.)

From Smithsonian Civil War: Inside the National Collection, edited by Neil Kagan.

In our Slate Academy on the history of American slavery, we’re trying hard to be specific about the shape of slavery in the United States—to go beyond a simple mental image of shackles, cotton, and plantations, and give this history some much-needed depth. To that end, here are a few demographic facts I discovered while researching the series that made me reconsider my previous assumptions.

Rebecca Onion Rebecca Onion

Rebecca Onion is a Slate staff writer and the author of Innocent Experiments

1. A comparatively tiny percentage of the total number of people carried off from Africa were brought to North America.

The American colonies were not the destination for most enslaved Africans. Fewer than 4 percent of captives taken from Africa by European ships between 1501 and 1867 disembarked in the North American colonies or the United States, write David Eltis and David Richardson in their Atlas of the Transatlantic Slave Trade. (This book is based on the Trans-Atlantic Slave Trade Database, which catalogs 35,000 voyages, or 80 percent of the total estimated trips.) The rest of those carried off ended up in the West Indies or South America.


2. One in 10 vessels involved in the slave trade may have experienced some kind of revolt or rebellion.

Eltis and Richardson estimate this number based on the documentation we retain, which is incomplete; in some countries, slave ship captains were not required to report on the happenings of their voyages, and in others, they were incentivized to minimize any violence that may have occurred.

The two further argue that the revolts (and the occasional attacks from the mainland on ships anchored off the African coast) truly impacted the profitability of the enterprise: “The threat of rebellion had a very real impact on costs. … Even unsuccessful revolts reduced the number of slaves carried off from Africa.” (More on this argument in their 2001 article, written with Stephen D. Behrendt, in the Economic History Review.)

3. For a few years, American ships—not English, or Portuguese—carried off one-quarter of the total number of captives taken from Africa.


While the American Revolution provoked a spate of state-level slave-trade bans, write Eltis and Richardson, “American traders experienced a resurgence of business” in the late 18th century. When South Carolina decided to allow the trade again in the early 19th century, owners of American ships, operating out of cities up and down the eastern seaboard, took full advantage. In 1806 and 1807—the window between the end of South Carolina’s ban and the advent of the federal prohibition against the international slave trade—“one-quarter of the captives from Africa sailed under the U.S. flag.” 

4. Slavery reached its peak in the Upper South in the last decade of the 18th century.

Lincoln Mullen, whose maps of the spread of U.S. slavery are based on census data gathered between 1790 and 1860, writes that slavery was at its peak in the Upper South—Virginia, North and South Carolina, Tennessee, Maryland, and Kentucky—between 1790 and 1800. As the 19th century went on, while slavery still persisted in those places, the states with the densest slave populations were to be found in the Deep South: Georgia, Alabama, and Mississippi.

5. People remained enslaved in “free” Northern states for a surprisingly long time.


In 1810, writes Ira Berlin (a guest on our first episode), there were still 27,000 enslaved people in the Northern “free states.” This happened because some of these states instituted gradualist emancipation policies, which delayed manumission until enslaved people had reached a certain age or served a certain number of years in an “indentured” arrangement, to pay for their freedom. As Harvey Amani Whitfield writes in his history of slavery in Vermont—a state that supposedly abolished the practice in 1777—the law was also unevenly and selectively enforced. Powerful people continued to hold servants in bondage 20 years after the passage of that state’s constitution.

6. Contrary to paternalist fictions, of the people forcibly removed westward between 1820 and 1860, most were sold, not brought along with families.

Mullen points to the work of historian Steven Deyle, who estimates that of a total number of 875,000 enslaved people who were removed from the Upper South to the Deep South between 1820 and 1860, 60 to 70 percent of those people were sold away—rather than emigrating southwest as part of a household. “In other words,” Mullen writes, “slavery was not the paternalist institution that its apologists made it out to be: it was an relentlessly exploitative system where the fundamental relation of owner to enslaved was defined by the markets.”

7. More than 1 million people were brought to the Americas from Africa in the middle decades of the 19th century, after European and American laws nominally terminated the international slave trade.


Eltis and Richardson tally 1,189,500 enslaved people who were taken from Africa, placed on illegal slave ships, and delivered to ports of the Americas between 1837 and 1867. (Portugal was the last European country to outlaw the transatlantic slave trade, in 1836.) Only 81,000 of those taken in this time period were retrieved from their captors and returned to Africa—mostly by British warships, which captured 90 percent of the small percentage of illegal slaving vessels that were stopped. (There was no guarantee the retrieved captives would end up back in their homes, however; many were “resettled” in the British colony of Sierra Leone.)

8. In the Deep South, the free black population was sparse indeed.

Looking at census data, Mullen found that most free black people lived on the eastern seaboard, or in the urban areas of the North. “Free African Americans,” he writes, “were almost entirely excluded, in part by an extensive system of patrols, from the majority slave populations of the Deep South.” This exclusion compounded the isolation of enslaved people in the Deep South, who would find it hard to reach sympathetic communities that might shield an escapee.

9. People who ran away from slavery tended to be male, and to come from the Upper South.

In his book Gateway to Freedom: The Hidden History of the Underground Railroad, Eric Foner (one of our guests for the upcoming Episode 8) writes that most runaways were men in their 20s. Women, who often had dependents relying on them, tended not to be able to leave as easily. And, of enslaved people who ran to Canada (the most popular destination for fugitives), most came from states that bordered the Mason-Dixon Line: “The Canadian census of 1861 found that 80 percent of southern-born blacks in Canada, many of them fugitive slaves and their children, had been born in only three states—Maryland, Virginia, and Kentucky.” (Of course, some people might have evaded census-takers, for obvious reasons, but the number is still quite suggestive.)

10. Some fugitives didn’t go north—they went south to Mexico.

Although enslaved people were less likely to have options for escape the further south they were taken, those who ended up in Texas could find refuge in Mexico, which abolished slavery in 1829. The Texas Runaway Slave Project, a database of advertisements and newspaper articles, contains many examples of ads for fugitives whose former owners were convinced they had fled south across the border. It’s difficult to know exactly how many enslaved people from Texas ended up in Mexico, but a contemporary source put the number at 4,000 in 1855.