Origins

The Atlantic slave trade emerged from the convergence of three 15th- and 16th-century developments: the existing trans-Saharan slave trade that had moved enslaved sub-Saharan Africans north into the Mediterranean Muslim world for nearly a millennium; the Portuguese exploration of West Africa in the 15th century, which gave European traders direct maritime access to African slave markets; and the demographic collapse of the indigenous Americas after 1492, which produced a labour shortage on the new European-administered plantation economies of the Caribbean and Brazil.

The first sustained Atlantic slave voyages began in the 1520s, transporting enslaved Africans from Portuguese West Africa to Spanish Caribbean sugar plantations. The system expanded substantially through the 16th and 17th centuries as Brazil (under Portuguese rule) became the largest sugar producer in the Atlantic world and the Caribbean (under Spanish, then English, French, and Dutch rule) developed its own sugar economy on a similar plantation model.

The Middle Passage

The forced transatlantic voyage — the Middle Passage — typically took six to eight weeks from West Africa to the Americas. Enslaved Africans were transported in cargo holds of European-built sailing vessels under conditions that historical demographic reconstruction now estimates produced an average mortality rate of approximately 14.5% per voyage. Cause of death was overwhelmingly disease (dysentery, smallpox, scurvy), supplemented by suicide, deliberate killing during slave rebellions on board, and conditions on the slaving ships that approximated mass-confinement disease transmission.

The systematic-quantitative reconstruction of the Atlantic slave trade is one of the major historiographical projects of the late 20th and early 21st centuries. The Slave Voyages database, compiled by an international team led by David Eltis, has now documented approximately 36,000 individual slave voyages from European, American, and African port records — approximately 80% of the total. The aggregate figures are: approximately 12.5 million Africans embarked from Africa, approximately 10.7 million survived to disembark in the Americas, and approximately 1.8 million died at sea during the Middle Passage.

The destinations

The Atlantic slave trade was, by volume, primarily a South American and Caribbean phenomenon. The conventional American image (probably 80% of English-language popular understanding of the trade) emphasizes the southern United States. The volumetric reality places the United States as a relatively minor destination:

  • Brazil: approximately 4.9 million enslaved Africans, primarily for sugar (until ~1820), gold (18th century), and coffee (19th century). Brazil was the largest destination of any single country.
  • Caribbean: approximately 4 million, of which the British Caribbean took approximately 1.8 million (Jamaica, Barbados, the Leeward Islands), the French Caribbean approximately 1.4 million (Saint-Domingue/Haiti, Martinique, Guadeloupe), the Spanish Caribbean approximately 800,000 (Cuba, Puerto Rico, Hispaniola), and the Dutch Caribbean a smaller number.
  • Spanish Mainland Americas: approximately 1.3 million, primarily to Mexico, Peru, and the gold-and-silver mining regions of the Andean and central Mexican territories.
  • British North America / the United States: approximately 390,000 — approximately 3% of the total Atlantic trade. The slave population of the antebellum United States (approximately 4 million by 1860) grew primarily by natural increase rather than by continued importation; the U.S. slave trade was a relatively small component of the total Atlantic operation.

African origins

The enslaved Africans transported across the Atlantic were drawn from a wide geographic range across West and Central Africa, with substantial regional variation by century. The major embarkation regions:

  • West Central Africa (modern Angola, Congo, Gabon): approximately 5.7 million — the largest single source region.
  • Bight of Benin (modern Benin, Togo, southwest Nigeria): approximately 2.0 million.
  • Bight of Biafra (modern southeast Nigeria, Cameroon): approximately 1.6 million.
  • Gold Coast (modern Ghana): approximately 1.2 million.
  • Senegambia (modern Senegal, Gambia): approximately 760,000.
  • Sierra Leone–Liberia coast: approximately 390,000.
  • Southeast Africa (Mozambique, Madagascar): approximately 540,000 (mostly later in the period).

The Africans were initially enslaved within Africa through warfare, raiding, judicial enslavement, and debt-bondage by African political entities; the European role at the African coast was substantially restricted to purchasing already-enslaved persons and transporting them across the Atlantic. The political-economic restructuring of West and Central African societies that the demand for trans-Atlantic slaves produced — the rise of slave-trading polities like Dahomey, the militarization of Asante, the demographic distortions of three centuries of slave export — was one of the most consequential indirect effects of the trade.

Abolition

The abolitionist movement against the Atlantic slave trade began in the late 18th century, driven by Quaker religious activism, Enlightenment political-philosophical argument, and substantial mobilization of British evangelical Protestant opinion. Denmark banned the trade in 1792 (effective 1803). The United States banned American participation in the trade as of 1 January 1808 (the earliest the Constitution permitted, under a 1787 compromise). Britain banned the trade by the Slave Trade Act of 25 March 1807, and over the following decades the Royal Navy’s West Africa Squadron intercepted approximately 1,600 illegal slaving vessels and freed approximately 150,000 enslaved Africans.

The institution of slavery itself was abolished in stages. The Haitian Revolution of 1791–1804 produced the first independent post-emancipation Black state. Britain abolished slavery throughout the empire by the 1833 Slavery Abolition Act (effective 1834, with apprenticeship through 1838). France abolished slavery in 1848. The United States abolished slavery through the 13th Amendment in 1865 after the Civil War. Brazil abolished slavery on 13 May 1888 — the last country in the Americas to do so. The Brazilian abolition is the conventional end of the institutional history of African chattel slavery in the western hemisphere.

Legacy

The Atlantic slave trade produced demographic, economic, and political consequences whose effects are still being studied. The African demographic loss — approximately 12.5 million people removed over 340 years, with substantial additional loss in the African wars and slave-raiding the trade incentivized — substantially distorted the long-term economic development of West and Central Africa. The descendants of the enslaved are the foundation of the modern African diaspora populations in Brazil, the Caribbean, the United States, and parts of Spanish America — approximately 200 million people in 2020.

The economic role of plantation slavery in the early modern Atlantic — the sugar economies of the Caribbean and Brazil, the coffee economies of Brazil, the cotton economy of the southern United States, the tobacco economy of Virginia — was a substantial component of the capital accumulation that financed the European Industrial Revolution. The historiographical question of how much of European industrial capital came from Atlantic slavery is contested but the substantive contribution is no longer denied.