The trans-Atlantic slave trade was the largest long-distance coerced movement of people in history and, prior to the mid-nineteenth century, formed the major demographic well-spring for the re-peopling of the Americas following the collapse of the Native American population. Cumulatively, as late as 1820, nearly four Africans had crossed the Atlantic for every European, and, given the differences in the sex ratios between European and African migrant streams, about four out of every five females that traversed the Atlantic were from Africa. From the late fifteenth century, the Atlantic Ocean, once a formidable barrier that prevented regular interaction between those peoples inhabiting the four continents it touched, became a commercial highway that integrated the histories of Africa, Europe, and the Americas for the first time. Slavery and the slave trade were the linchpins of this process. With the decline of the Native American population, labor from Africa formed the basis of the exploitation of the gold and agricultural resources of the export sectors of the Americas, with sugar plantations absorbing well over two thirds of slaves carried across the Atlantic by the major European and Euro-American powers. For several centuries, slaves were the most important reason for contact between Europeans and Africans.


Diagram of a slave ship’s interior showing where the enslaved Africans were held during the voyage. Source: Wikimedia Commons

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Watch historians discuss our growing understanding of the African slave trade.

The Enslavement of Africans

A revolution in ocean-going technology gave Europeans the ability to have continuous access to remote peoples and move them against their will over very long distances. Slavery, which had disappeared from northwest Europe long before this point, exploded into a far greater significance and intensity than it had possessed at any point in human history. The major cause was a dissonance in African and European ideas of eligibility for enslavement at the root of which lies culture or societal norms, not easily tied to economics. Without this dissonance, there would have been no African slavery in the Americas. The slave trade was thus a product of differing constructions of social identity and the ocean-going technology that brought Atlantic societies into sudden contact with each other.

The trans-Atlantic slave trade grew from a strong demand for labor in the Americas, driven by consumers of plantation produce and precious metals, initially in Europe. Because Native Americans died in large numbers, and insufficient numbers of Europeans were prepared to cross the Atlantic, the form that this demand took was shaped by conceptions of social identity on four continents, which ensured that the labor would comprise mainly slaves from Africa.

But the central question of which peoples from Africa went to a given region of the Americas, and which group of Europeans or their descendants organized such a movement cannot be answered without an understanding of the wind and ocean currents of the North and South Atlantics. There are two systems of wind and ocean currents in the North and South Atlantic that follow the pattern of giant wheels – one lies north of the equator turns clockwise, while its counterpart to the south turns counterclockwise. The northern wheel largely shaped the north European slave trade and was dominated by the English. The southern wheel shaped the huge traffic to Brazil which for three centuries was almost the almost exclusive preserve of the largest slave traders of all, the Portuguese.

Winds and currents thus ensured two major slave trades – the first rooted in Europe, the second in Brazil. Winds and currents also ensured that Africans carried to Brazil came overwhelmingly from Angola, with southeast Africa and the Bight of Benin playing smaller roles, and that Africans carried to North America, including the Caribbean, left from mainly West Africa, with the Bights of Biafra and Benin and the Gold Coast predominating. Just as Brazil overlapped on the northern system by drawing on the Bight of Benin, the English, French, and Dutch carried some slaves from northern Angola into the Caribbean.


This map shows the prevailing wind currents in the world’s oceans (Source: Wikimedia)

African Agency and Resistance

If demand for slave-grown produce, social identity, and the Atlantic environment were three key factors shaping the traffic, the agency of Africans comprised a fourth major influence. The merchants who traded slaves on the coast to European ship captains – for example, the Vili traders north of the Congo, the Efik in the Bight of Biafra – and behind them the groups that supplied the slaves, such as the Kingdom of Dahomey, the Aro network, and further south, the Imbangala, all had strict conceptions of what made an individual eligible for enslavement. Among such criteria were constructions of gender, definitions of criminal behavior, and conventions for dealing with prisoners of war. The make-up of slaves purchased on the Atlantic coast thus reflected whom Africans were prepared to sell as much as whom Euro-American plantation owners wanted to buy.

But the victims of the slave trade also had a major impact on the trade. Probably about one in ten slaving voyages experienced major rebellions, of which the attempts to control increased the costs of a slave voyage to the point where far fewer slaves entered the traffic than would have been the case without resistance. In addition, vessels from some regions on the coast appear to have been more prone to experience slave uprisings than those from other regions. The rebellion-prone areas were precisely those regions, broadly comprising Upper Guinea (Senegambia, Sierra Leone, and the Windward Coast) which had the least participation in the slave trade. The strong inference is that European slave traders avoided this part of the African coast except in those years when demand for slaves, and their prices, were particularly high.

Early Slaving Voyages

With the key forces shaping the traffic briefly described, we can now turn to a short narrative of the slave trade. The first Africans forced to work in the New World left from Europe at the beginning of the 16th century, not from Africa. There were few vessels that carried only slaves on this early route, so that most would have crossed the Atlantic in smaller groups on vessels carrying many other commodities, rather than dedicated slave ships. Such a slave route was possible because an extensive traffic in African slaves from Africa to Europe and the Atlantic islands had existed for half a century before Columbian contact, such that ten percent of the population of Lisbon was black in 1455, and black slaves were common on large estates in the Portuguese Algarve.

The first slave voyage direct from Africa to the Americas probably sailed in 1526. Before mid-century, all trans-Atlantic slave ships sold their slaves in the Spanish Caribbean, with the gold mines in Cibao on Hispaniola emerging as a major purchaser. Cartagena, in modern Columbia, appears as the first mainland Spanish American destination for a slave vessel – in the year 1549. On the African side, the great majority of people entering the early slave trade came from the Upper Guinea coast, and moved through Portuguese factories initially in Arguim, and later the Cape Verde islands. Nevertheless, the 1526 voyage set out from the other major Portuguese factory in West Africa – Sao Tome in the Bight of Biafra – though the slaves almost certainly originated in the Congo.

The slave traffic to Brazil, eventually accounting for about forty percent of the trade, got underway around 1560. Sugar drove this traffic, as Africans gradually replaced the Native American labor force on which the early sugar mills (called engenhos) had drawn over the period 1560 to 1620. By the time the Dutch invaded Brazil in 1630, Pernambuco, Bahia, and Rio de Janeiro were supplying almost all of the sugar consumed in Europe, and almost all the slaves producing it were African. By 1640, there were two major branches of the trans-Atlantic slave trade operating, one to Brazil, and the other to the mainland Spanish Americas, but together they accounted for no less than 7,500 departures a year from the whole of sub-Saharan Africa, almost all of them by 1600 from west-central Africa. The sugar complex spread to the eastern Caribbean from the beginning of the 1640s. Sugar consumption steadily increased in Europe, and the slave system began two centuries of westward expansion across tropical and sub-tropical North America. At the end of the seventeenth century, gold discoveries in first Minas Gerais, and later in Goias and other parts of Brazil, began a transformation of the slave trade which triggered further expansion of the business. In Africa, the Bights of Benin and Biafra became major sources of supply, in addition to Angola, and were joined later by the more marginal provenance zones of Sierra Leone, the Windward Coast, and South-east Africa. The volume of slaves carried off reached thirty thousand per annum in the 1690s and eighty-five thousand a century later. More than eight out of ten Africans pulled into the traffic in the era of the slave trade made their journeys in the century and a half after 1700.

Click and Explore

Visit the Slave Voyages website to view maps showing both where slaves were taken from and where they were taken.

The African Side of the Trade

On the African side, the sheer human and environmental diversity of the continent makes it difficult to examine the trade from Africa as a whole. The slave trade did not expand, nor, indeed, decline, in all areas of Africa at the same time. Rather, a series of marked expansions (and declines) in individual regions contributed to a more gradual composite trend for sub-Saharan Africa as a whole. Each region that exported slaves experienced a marked upswing in the number of slaves it supplied for the trans-Atlantic trade and, from that point, the normal pattern was for a region to continue to export large numbers of slaves for a century or more. The three regions that provided the fewest slaves – Senegambia, Sierra Leone, the Windward Coast – reached these higher levels for much shorter periods.

By the third quarter of the eighteenth century, all regions had undergone an intense expansion of slave exports. A cargo of slaves could be sought at particular points along the entire Western African coast. As the Brazilian coffee and sugar boom got under way near the end of the eighteenth century, slavers rounded the Cape of Good Hope and traveled as far as southeast Africa to fill their vessels’ holds. But while the slave trade pervaded much of the African coast, its focus was no less concentrated in particular African regions than it was among European carriers. West Central Africa, the long stretch of coast south of Cape Lopez and stretching to Benguela, sent more slaves than any other part of Africa every quarter century with the exception of a fifty-year period between 1676 and 1725. From 1751 to 1850, this region supplied nearly half of the entire African labor force in the Americas; in the half century after 1800, West Central Africa sent more slaves than all of the other African regions combined. Overall, the center of gravity of the volume of the trade was located in West Central Africa by 1600. It then shifted northward slowly until about 1730, before gradually returning to its starting point by the mid-nineteenth century.

Further, slaves left from relatively few ports of embarkation within each African region, even though their origins and ethnicities could be highly diverse. Although Whydah, on the Slave Coast, was once considered the busiest African slaving port on the continent, it now appears that it was surpassed by Luanda, in West Central Africa, and by Bonny, in the Bight of Biafra. Luanda alone dispatched some 1.3 million slaves, and these three most active ports together accounted for 2.2 million slave departures. The trade from each of these ports assumed a unique character and followed very different temporal profiles. Luanda actively participated in the slave trade from as early as the 1570s, when the Portuguese established a foothold there, through the nineteenth century. Whydah supplied slaves over a shorter period, for about two centuries, and was a dominant port for only thirty years prior to 1727. Bonny, probably the second largest point of embarkation in Africa, sent four out of every five of all the slaves it ever exported in just the eighty years between 1760 and 1840. It is not surprising, therefore, that some systematic links between Africa and the Americas can be perceived.

As research on the issue of trans-Atlantic connections has progressed, it has become clear that the distribution of Africans in the New World is no more random than the distribution of Europeans. Eighty percent of the slaves who went to southeast Brazil were taken from West Central Africa. Bahia traded in similar proportions with the Bight of Benin. Cuba represents the other extreme: no African region supplied more than 28 percent of the slave population in this region. Most American import regions fell between these examples, drawing on a mix of coastal regions that diversified as the trade from Africa grew to incorporate new peoples.

The Middle Passage

Whatever the route taken, conditions on board reflected the outsider status of those held below deck. No European, whether convict, indentured servant, or destitute free migrant, was ever subjected to the environment which greeted the typical African slave upon embarkation. The sexes were separated, kept naked, packed close together, and the men were chained for long periods. No less than 26 percent of those on board were classed as children, a ratio that no other pre-twentieth century migration could come close to matching. Except for the illegal period of the trade when conditions at times became even worse, slave traders typically packed two slaves per ton. While a few voyages sailing from Upper Guinea could make a passage to the Americas in three weeks, the average duration from all regions of Africa was just over two months. Most of the space on a slave ship was absorbed by casks of water. Crowded vessels sailing to the Caribbean from West Africa first had to sail south before turning north-west and passing through the doldrums.


The author of this account was Olaudah Equiano who was kidnapped from his family when he was 11 years old and sold into slavery in Virginia. In 1766, he bought his own freedom. He wrote his Memoir to show people the evils of slavery in the 18th century. In this excerpt, he describes the horrors of the slave ship:

I was soon put down under the decks, and there I received such a salutation in my nostrils as I had never experienced in my life: so that, with the loathsomeness of the stench, and crying together, I became so sick and low that I was not able to eat, nor had I the least desire to taste anything. I now wished for the last friend, Death, to relieve me; but soon, to my grief, two of the white men offered me eatables; and, on my refusing to eat, one of them held me fast by the hands, and laid me across, I think, the windlass, and tied my feet, while the other flogged me severely. I had never experienced anything of this kind before, and, although not being used to the water, I naturally feared that element the first time I saw it, yet, nevertheless, could I have got over the nettings, I would have jumped over the side, but I could not; and besides, the crew used to watch us very closely who were not chained down to the decks, lest we should leap into the water; and I have seen some of these poor African prisoners most severely cut, for attempting to do so, and hourly whipped for not eating.

Read a larger extract of his Memoir here.

Throughout the slave trade era, filthy conditions caused slaves to suffer serious endemic gastro-intestinal diseases. These, together with periodic breakouts of violent resistance, meant that between 12 and 13 percent of those forcibly enslaves on ships did not survive the voyage. Crew mortality as a percentage of those going on board matched slave mortality over the course of the voyage, but as slaves were there for a shorter period of time than the crew, mortality rates for slaves (over time) were more severe. The 16th-century world was violent, and life-expectancy was short everywhere, but the human misery quotient generated by the forced movement of millions of people in slave ships cannot have been matched by any other human activity.

The Trade’s Influence on Ethnic and Racial Identity

In the Atlantic after 1492, oceans that had hermetically sealed peoples and cultures from each other sprouted sea-lanes almost overnight. Cultural accommodation between peoples, in this case between Europeans and non-Europeans, always took time. The big difference was that before Columbus, migrations had been gradual and tended to move outwards from the more to the less densely populated parts of the globe. But Columbian contact was sudden, and inhibited any gradual adjustment, cultural as well as epidemiological. A merging of perceptions of right and wrong, group identities, and relations between the sexes, to look only at the top of a very long list of social values, could not be expected to occur quickly in a post-Columbian world. In short, cultural adjustment could not keep pace with transportation technology.

During the long coercive interlude of forced trans-Atlantic migration European and African conceptions of self and community (and eligibility for enslavement) did not remain static. On the African side, the major effect of the African-European exchange was to encourage an elementary pan-Africanism, at least among victims. The initial and unintentional impact of European sea-borne contact was to force non-elite Africans to think of themselves as part of a wider African group. Initially, this group might be Igbo, or Yoruba, and soon, in addition, blacks as opposed to whites. On board a slave ship with all the slaves always black, and the crew largely white, skin color defined ethnicity.


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