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Illegal Slave Trade


Different branches of the slave trade across the Atlantic Ocean became illegal at different times. "Illegal" has two connotations in this context. Introducing slaves into a region (or removing them) in contravention of the laws of that region certainly qualifies, but so does buying or selling them in a region where it is still legal to do so–if the slave trader himself belongs to a country that has prohibited its citizens from carrying on the traffic. Thus, the Rhode Island slave traders who searched out markets outside the U.S. in the late eighteenth century–as one state after another outlawed the traffic–were probably the first illegal traders, if we set aside those merchants who smuggled African captives from the very outset of the Atlantic slave trade.

From the 1780s until the last slave ship arrived in Cuba in 1867, the illegal portion of the traffic grew steadily until it encompassed the whole of the slave trade. The precise point at which this happened is unclear, but it was probably in 1836. By then, all the major plantation areas of the Americas had prohibited arrivals from Africa, but some countries still allowed their citizens to participate in such activity. Much slave trading was in contravention of treaties rather than laws, and the sanctions entailed confiscation of property rather than fines, imprisonment, or death.

Conventionally, "illegal" slave trading has been taken to cover arrivals in the British Caribbean after May 1807, in the U.S. after January 1, 1808, in the French Americas after 1818, in the Spanish Caribbean after 1820, and in Brazil after 1830. By this definition, about 1.5 million Africans — a large number of them children — arrived illegally in the Americas–that is, about 15 percent of the people who remained alive at the end of the Middle Passage during the whole slave-trade era. In fact, the decade from 1836 to 1845 was actually one of the busiest, and as this suggests, the slave trade did not decline gradually, nor did slave owners decide they no longer wanted enslaved labor. Rather, some form of prohibition was essential to the trade's disappearance.

The Economics of the Illegal Slave Trade

The illegal slave trade was driven by rising demand for plantation products, mainly in Europe, and steady improvements in the productivity of the enslaved population, which in turn increased the value (and therefore the price) of coerced labor. The three major slave economies of the world in the mid-nineteenth century were the U.S., Brazil, and Cuba; their economic expansion was dramatic, and they dominated the world output of cotton, coffee, and sugar, respectively.

The U.S. saw its slave population quadruple between 1790 and 1860 from natural increase rather than the arrival of Africans. By contrast, the people of African descent in Brazil and Cuba experienced either negative or very small positive natural population growth. About 800,000 Africans came into Cuba over the same period that the U.S. enslaved population quadrupled, and about 2.2 million arrived in Brazil. The slave trade became illegal midway through this inflow, and one way of seeing its importance is to recognize that the inflow provided for the Cuban and Brazilian planters what natural increase generated for the U.S. planters–a supply of coerced labor that supported world dominance in a single product. In the U.S. and British Caribbean, relatively few Africans arrived after 1807.

Behind this pattern lay a dramatic increase in the spread between the prices of captives in Africa and slaves in the Americas. As native-born slaves became more productive in the Americas in the nineteenth century, the price of even unskilled individuals rose above $1,000 in the U.S. South, Cuba, and Brazil alike. On the African coast, by contrast, prices declined with the volume of the traffic. On the Congo River in the 1860s, it was possible to buy a young adult male for $30, and after 1807, prices at the point of embarkation were always below $100. Historians have often compared prices on either side of the Atlantic and called the difference "profits," as though transportation and risk did not exist. In fact, illegal slave trading could be extremely costly. Slave vessels avoided established ports and the facilities they offered. Their owners obtained fraudulent (and thus expensive) registration papers. The ships themselves were faster than most other vessels, and often a single venture involved more than one ship, as owners sent out goods and equipment on a different ship as a subterfuge.

Slave trading in its final stage entailed increased risks of capture, more costly delays on the African coast, higher shipboard mortality for the victims, and, most important in financial terms, considerable bribes to officials of the region into which the Africans were introduced. As with the modern trade in illegal drugs, potential profits were high (though they were never simply the price of the enslaved person in the Americas, less the price of the captive in Africa), but so were potential losses. Some of the largest slave traders went bankrupt, including Pedro Blanco, whose name is associated with nearly fifty voyages to Cuba before 1845; he assumed the role of captain, owner, and factor on the coast of Africa –mostly Sierra Leone and Liberia–at different times in his long career.

In some sense, the voyage itself and the captain became much less the center of the overall operation than was the case in earlier centuries. In major markets such as Whydah in Benin and Lagos, Nigeria, it was still possible for a transatlantic vessel to seek captives without prior arrangement, but on most of the coast more elaborate and costly organizational structures were required. The captain's role became less important and the key slave trading personnel operated on shore, on both sides of the Atlantic, rather than on the vessel itself. The major decisions on bringing together (or "bulking") the required number of captives, assembling provisions and equipment, and timing the departure were now made on land.

In the Americas, knowing which officials to bribe and trying to dispose of captives in open-market conditions to maximize returns became more difficult than in the pre-suppression era and required more manpower and a different set of skills. On the voyage itself, captains might find themselves sailing an empty ship out to the African coast, or at least one without the fittings of a slave ship, given that the discovery of such equipment on board increased the risk of conviction in a court of law. Barrels for water (which always occupied by far the largest amount of space on a transatlantic slave vessel), planks for slave decks, irons, a large boiler for cooking, and the provisions themselves were frequently loaded in Africa just prior to departure. In the last few decades of the illegal slave trade, the complete shipment was frequently rushed on board just before leaving for the Americas.

Changes in Regions of Provenance

On the African coast, pronounced shifts in both regions of provenance and the strategies of slave traders occurred during the illegal era. The slave trade had not evolved in all areas of Africa at the same time, nor, indeed, did it decline uniformly in response to attempts to suppress it. The sheer human and environmental diversity of sub-Saharan African societies made such an outcome unlikely. Rather, a series of marked or stepped declines in individual regions contributed to a more gradual trend for sub-Saharan Africa as a whole. Although the overall dominance of West-Central Africa in the transatlantic slave trade is well recognized, it is not generally appreciated how important the region was in its last half century. In this period, that area dispatched more people than all other regions combined.

Reviewing the patterns of the traffic from north to south, we can see that in Upper Guinea (Senegambia, Sierra Leone, and the Windward Coast) slave trading gradually declined after 1820 before ending rather suddenly in the early 1840s, though it ended first on the Windward Coast.

On the Gold Coast, departures after 1820 were occasional and never more than a few hundred a year, but a further forty years passed before the traffic ended completely. In the Bight of Benin, traffic peaked in the first half of the eighteenth century. It was nevertheless the part of West Africa where the slave trade persisted longest. Almost all the captives leaving the region after 1830 passed through Lagos and Whydah, with the latter port remaining active into the mid-1860s. In the adjacent Bight of Biafra region, by contrast, the traffic ended in the early 1840s, while the relative role of southeast Africa, heavily involved in the Indian Ocean slave trade, increased in the closing half century of the transatlantic traffic. Overall, in the nineteenth century, the center of the slave trade from sub-Saharan Africa shifted strongly southward.

A Shift in Ethnicities

These patterns held considerable implications for the ethnolinguistic composition of the illegal slave trade. The mix of peoples in the Upper Guinea trade continued to be highly diverse in the illegal era. The largest group was Mende, but Koronko, Mandingo, Susu, Temne, and Fula were well represented. These six groups made up 80 percent of a sample of one thousand captives taken from Galinhas (Guinea-Bissau) and Rio Pongo (Guinea) in the 1820s and 1830s; three-quarters of these captives came from areas less than 150 miles from the coast. In the eighteenth century, peoples from the middle and upper regions of the Gambia and Senegal rivers would have been much more heavily represented.

In the Bight of Benin, Yoruba peoples, scarcely noticeable in an earlier era, dominated those passing through Whydah and Lagos, with some Hausa and Nupe among them. The counterparts to the Yoruba in the Bight of Biafra were Igbo peoples, perhaps accounting for as much as 60 percent of deportees from the region, but in this case the pattern was not new. Ibibio and the numerous small ethnic groups of the Niger Delta made up the remainder. Further east, the Cameroons Highlands was almost the exclusive source of slaves leaving from what is now the Republic of Cameroon.

New research on the huge West-Central Africa region suggests that the old picture of long-distant trade networks and the central importance of the Lunda Empire (northeastern Angola and western Congo) is in need of revision. Data from slave registers in the Portuguese colonies and from registers of liberated Africans in Havana and Sierra Leone indicate that the majority came from areas much closer to the coast than was previously thought. Overall, there seems to have been a shift toward the coast as the source for captives in the nineteenth century.

One further pattern to emerge after 1800 was an increase in the share of Muslims, almost all of them passing through ports located in the Bight of Benin, such as Lagos and Whydah, and comprising mainly Hausa and Yoruba. A preliminary analysis of a large database of Africans (including their names) who were taken off slave ships by British naval cruisers between 1821 and 1841 and liberated in Sierra Leone and Havana suggests that one-fifth of those leaving the Bight of Benin were Muslims, many of them women.

Changes in the Trading Centers

Attempts to suppress the slave trade triggered a marked strategic shift in trading locations toward the end. In the eighteenth century, the trading centers had been islands in Upper Guinea, forts on the Gold Coast, and, further east and south, enclaves of strong African authority in places such as Whydah, Bonny, Old Calabar, and the Vili centers of northern Angola, or centers of European authority in the case of Luanda, Benguela, and Mozambique to the south. Slave traders, like other merchants, sought physical security and a known set of rules to carry on business.

In the era of attempted naval suppression, both the islands and forts proved too susceptible to naval interference, and trafficking shifted to creeks and mangrove swamps in Upper Guinea. In the area of the castles on the Gold Coast there was no obvious alternative, and the slave trade ended quickly in the region. In the Bight of Benin, a lagoon system, and in the Bight of Biafra the myriad waterways of the Niger Delta allowed captives to be moved quickly to points of embarkation beyond the knowledge of patrolling cruisers, and thus a clandestine trade survived longer there.

Further south, the vast Congo River estuary offered better cover for slave traders than the Vili ports of Cabinda and Malembo, and replaced them in the last thirty years of the trade. Beginning in the mid-1830s, Portuguese government actions in Angola and Mozambique forced traffickers to conduct their affairs and embark their captives from secluded creeks and beaches removed from these government centers, in Luanda's case often as far away as the Congo.

From the Barracoon to the Middle Passage

From the perspective of the African captives, conditions under which they were forced to make their journey from the point of enslavement to a plantation in the New World probably worsened. Once the trade was illegal, they often spent long periods of time awaiting embarkation, as slave ships waited for cruisers to leave the area. Food for hundreds of people could run short, and confinement in a barracoon was no healthier than in a slave ship, at least in terms of the epidemiological environment. If they survived a potentially long wait in the pens, the captives in the illegal era might expect a more rapid transatlantic crossing than their predecessors.

Voyage length from Angola to the Caribbean, for example, fell from just under ten weeks in the mid-eighteenth century to six weeks one hundred years later. On the other hand, southeast Africa became relatively more important in the nineteenth century, and the much longer voyages that were typical of this region offset some of this effect on the average experience. Indeed, the longest Middle Passage ever recorded in terms of distance–from near Mombasa in east Africa to Cuba–took place in this era.

At the outset of the illegal period, owners used smaller, faster vessels than previously, and they increased the number of captives per ton. But this pattern shifted after 1850, when much larger vessels came into use and the people per ton ratio fell once more. Twenty-five steamers are known to have gone to Africa for captives after 1840, and 80 percent of all vessels recorded as carrying off more than one thousand people on a single voyage sailed after 1830. After allowing for faster voyage times, shipboard mortality–that is, deaths per day–increased in the illegal phase of the traffic (after declining steadily since the seventeenth century). The worsening mortality may well have been the result of poorer conditions on land prior to embarkation. The gastrointestinal diseases that gave survivors of the Middle Passage such a skeletal appearance probably began before they got on board.

A New Demography

One striking and under-recognized feature of the illegal slave trade was a shift in its demographic composition. Over two centuries of the traffic there was a steady climb in the share of males. The male ratio increased from 55 percent in the mid-seventeenth century to nearly 75 percent in the last quarter century of the trade. But a more dramatic change occurred in the share of children. Between the last fifteen years of the eighteenth century and the final era of the slave trade, 1851-67, that share more than doubled, to 43 percent, and several slave ships carried only children. The rise in the male ratio was largely accounted for by boys rather than men, and as the adult ratio fell and the proportion of males increased, the volume of women carried across the Atlantic fell both absolutely and relatively to its lowest recorded level in this era.

More broadly, in Atlantic migration as a whole, this period saw European women come to predominate numerically over African women for the first time in the "re-peopling of the Americas." Taking together as a unit coerced African migrants and free and indentured European migrants, it might be said that whereas four out of five women crossing the Atlantic before 1820 had been African, this ratio was reversed in the middle decades of the nineteenth century as mass migration from Europe got under way.  The reasons behind these patterns are still not clear. As for children, perhaps, they were easier to smuggle into the Americas, in that they blended into large plantations more easily. But such patterns may well have more to do with social structures and attitudes in Africa than changes in the conditions of transportation and in what slave owners in the Americas were demanding in the way of labor.

But whatever the cause, the consequences in cultural terms must have been considerable and have so far been ignored. One immediate impact of these changes was a sharp decline in rebellions aboard slave ship. The greatest incidence of revolts occurred in the third quarter of the eighteenth century. However, while the rate declined, it might be noted that the most successful shipboard revolt in the history of the slave trade occurred in 1859, when three hundred Africans overpowered the crew of a French vessel, successfully returned the ship to the Windward Coast, and disembarked with few casualties. 

No Longer a Triangular Trade

Except for the revived French traffic, which operated out of the ports of France between 1813 and 1831, illegal slave ships were owned and voyages organized overwhelmingly in the Americas. At least seven thousand ventures sailed for Africa from ports in Brazil and Cuba after 1820, with Havana, Bahia, and Rio de Janeiro predominating. Slave vessels also left from U.S. ports after 1840.

How many were owned by Americans is unclear, but there were at least two voyages bringing Africans to the U.S.

Others were purchased and fitted out in the U.S. but owned by Portuguese and Spanish nationals. Ownership of transatlantic slaving ventures had always been broadly based, but became even more so in the nineteenth century as investors sought to spread risk in the face of attempts to suppress the trade. In Havana, a nascent stock exchange operated in the 1830s, where the shares of ventures were traded down to the moment of the return of the vessel. Shopkeepers and local tradesmen participated in this, although plantation owners and merchants based in Spain were the source of most of the funds invested in the Cuban slave trade.

In Brazil, Portuguese merchants formed the largest single group of investors. But some of the funding ultimately came from Britain. By the second quarter of the nineteenth century, the manufactured goods carried to the coast to exchange for captives were largely made in Britain, and in both Brazil and Cuba goods were advanced on credit by British merchants, with payment due at the end of the slaving voyage. Alcohol and tobacco, the produce of the Americas, formed a large share of the remainder of the outbound cargo, particularly in Brazil. Many British citizens were thus benefiting from the illegal traffic even as the British navy and the Foreign Office led the campaign against it.

As the treaty network spread and governments in the Americas slowly began to pass and enforce measures against the slave trade, it becomes more difficult to discern ownership. In the 1840s vessels often sailed without any registration papers, or alternatively they carried sets of papers (and flags) of more than one country. These would be changed in response to naval activity; even more often, the U.S. flag, of which the British were wary, would be used on the outbound voyage and some other flag (or no flag at all) would be hoisted once the captives were taken on board.

The Impact of the Suppression

Making the slave trade illegal did not immediately bring it to an end, but it did change the way in which the traffic was carried on. It reduced the length of the average voyage, as slave traders sought ships that could outsail naval vessels, but it also increased rates at which captives died. Illegality tended to reduce the prices of captives at the point of purchase on the African coast, but it also increased their cost in the Americas by raising the transportation and distribution costs of getting them to markets in the Americas.

The overall impact of attempts to suppress the slave trade was to reduce the number of people carried off from Africa, as well as to keep the price of the plantation produce at levels higher than would have been the case in the absence of suppression. It was also responsible for the gradual drift southward of the slave trade. Brazil, Angola, and southeast Africa were of far greater relative importance after 1820 than they had been at any time since the mid-seventeenth century. Northern Europe largely disappeared as an organizational base of the traffic, though it continued to supply merchandise and ships.

Other striking features of the last phase of transatlantic slave trading, such as the age and gender shifts and the different ethnic composition of coerced migrants, are less easy to associate with suppression. But whatever the ultimate costs and impact of suppression, presumably no one today would agree with those mid-nineteenth-century observers who argued that attempts to end the trade forcibly were hopeless, that they caused more African deaths than African lives saved from the traffic, and that they should be halted immediately.

David Eltis
Robert W. Woodruff Professor of History
Emory University


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Eltis, David. Economic Growth and the Ending of the Transatlantic Slave Trade. New York: Oxford University Press, 1987.

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