Transatlantic Slave Trade
The forced shipment of roughly 12.5 million enslaved Africans to the Americas, history's largest forced migration and an engine of the Atlantic economy.
Between the early 1500s and 1866, European and American slavers forced roughly 12.5 million Africans across the Atlantic in the holds of ships. About 10.7 million survived the crossing; the rest died at sea. It was the largest forced migration in human history, and it was not an accident of commerce but its central mechanism, an entire economy built on the ownership of human beings.
The triangle
The trade ran as a triangle across the ocean. Ships left European ports such as Liverpool, Nantes, and Lisbon carrying manufactured goods: textiles, firearms, iron, alcohol. On the West African coast these were exchanged for captive people, most of them seized in the interior through war, raiding, and debt bondage, then sold to Europeans by African merchants and states who controlled access to the coast. The captives were carried west and sold in the Americas. The ships returned to Europe loaded with the plantation goods that slave labor produced: sugar above all, then tobacco, cotton, coffee, and rum. Portugal and Brazil carried the largest share of all, close to half of the total, followed by Britain, with the Spanish, French, and Dutch taking most of the rest. Each leg turned a profit, and the whole circuit pumped capital into Atlantic ports, banks, insurers, and shipyards. Historians still argue over exactly how much this financed the Industrial Revolution, but no one disputes that it built cities and fortunes.
The Middle Passage
The Atlantic crossing, the Middle Passage, is the stretch the Brookes diagram made impossible to forget. Captives were packed below decks in spaces sometimes under two feet of headroom, chained, and held for roughly six to ten weeks in filth and darkness. Dysentery, smallpox, and dehydration were routine; suicide and revolt were not rare. Shipboard mortality averaged around 15 percent by the late eighteenth century, down from roughly a third in the sixteenth, an 'improvement' driven not by mercy but by the logic of protecting cargo. Those who survived were sold into plantation slavery, branded, worked, and frequently broken in the sugar fields of Brazil and the Caribbean, which together absorbed the great majority of the enslaved. Only a small share, around 4 percent, ever reached what became the United States.
The long shadow
Abolition came slowly and unevenly. Britain banned the trade in 1807 and slavery itself in the 1830s; the United States outlawed the trade in 1808 but kept slavery until 1865; Brazil, the largest importer of all, ended slavery only in 1888. Having led the trade for a century, Britain then spent decades using the Royal Navy to suppress it, patrolling the African coast and intercepting hundreds of slave ships. The trade's wealth compounded on one side of the ocean and its costs on the other. West and Central Africa lost millions of people in their most productive years, saw states militarized around slave-raiding, and entered the colonial era demographically and politically damaged. The plantation societies of the Americas were built on a racial caste that outlasted slavery by generations. The ships stopped sailing in the 1860s. The ledger they opened, wealth on one shore and loss on the other, has never fully closed.