Atlantic Slave Trade

Summary

From the early 16th century to the 1860s, European and American traders forcibly transported an estimated 12.5 million Africans across the Atlantic Ocean into slavery in the Americas, in a trade organized around chartered national trading companies, plantation economies, and legal systems that treated enslaved people as property across generations. An estimated 1.8 million people died during the Middle Passage crossing alone.

What Happened

Beginning in the early 16th century, European traders — first Portuguese and Spanish, later joined by Dutch, French, British and other national trading operations, often organized through chartered companies granted monopoly trading rights by their governments — established a trade in enslaved Africans transported to plantation and mining economies across the Americas. Captives were typically obtained through raids, warfare, and purchase from African intermediaries and states operating along the West and Central African coast, marched to coastal fortifications and ports, and held before being loaded onto ships for the transatlantic crossing known as the Middle Passage^[2]. Conditions aboard slave ships were extreme: captives were typically shackled below deck with minimal space, food and sanitation, producing high rates of disease and death documented across thousands of individual voyage records^[1]. The trade continued for more than three centuries, with the last documented transatlantic slaving voyages occurring in the 1860s, decades after Britain (1807) and the United States (1808) had formally banned the importation trade itself, though not, initially, slavery as an institution.

Who Was Affected

An estimated 12.5 million Africans were forcibly embarked for the Americas over the trade’s duration, drawn from a wide range of West and Central African societies and ethnic groups; the trade’s demographic impact on the affected regions, including its role in regional warfare and population loss, remains a significant and continuing subject of African historical scholarship distinct from this file’s Americas-side focus.

Who Was Responsible

Responsibility for organizing, financing and profiting from the trade rested principally with European trading companies and, from the colonial and early national periods onward, American shipping and mercantile interests, operating under licenses, charters and legal protections granted by their respective governments; plantation owners and colonial legal systems in the Americas sustained the institution of slavery across generations after arrival. Some African states and traders also participated directly in supplying captives to coastal traders, a documented historical fact that does not diminish the responsibility of the trade’s European and American organizers and beneficiaries, who created and sustained the market, financing, shipping and legal infrastructure that made the trade possible at this scale.

The Justification

Slaveholding societies developed an extensive legal and ideological apparatus to justify the institution, including claims of racial hierarchy, religious argument (selectively invoking scripture), and simple assertion of enslaved people’s status as property under civil law. These justifications were contested from the trade’s early centuries by enslaved people themselves, free Black abolitionists, and a growing abolitionist movement from the late 18th century onward.

Ideas Behind the File

The trade is documented in this archive as the foundational case of slaveholding ideology — the body of legal and social doctrine that defined enslaved people as property — operating within the broader economic system of plantation capitalism, which organized Atlantic-world agricultural production around enslaved labor.

Institutions

National chartered trading companies (including, at various points, England’s Royal African Company and comparable Dutch, French and Portuguese entities) organized much of the early trade under government-granted monopoly rights; colonial and later national legal systems across the Americas codified and enforced slavery as a civil institution for generations after individual transport voyages ended.

What Is Certain

That European and American traders forcibly transported an estimated 12.5 million Africans across the Atlantic under conditions producing substantial mortality during the crossing, and that this trade was legally sanctioned and economically central to Atlantic-world colonial economies for over three centuries, are established beyond serious dispute by extensive shipping, customs, and legal records compiled across national archives and systematized in the Voyages database^[1].

Human Consequences

Beyond the direct mortality of the Middle Passage, survivors and their descendants were subjected to chattel slavery across generations, including family separation, forced labor, and systematic denial of legal personhood, with consequences addressed in later Files across this archive’s Slavery & Racial Violence collection.

Accountability

Britain’s Slave Trade Act (1807) and Slavery Abolition Act (1833) ended the trade and slavery across most of the British Empire, respectively, though the latter compensated slave owners, not enslaved people, for their financial loss — a debt the UK government did not finish repaying until 2015. The United States banned the importation trade in 1808 but did not abolish slavery itself until the Thirteenth Amendment in 1865, following the Civil War. No comprehensive international reparations process has been established for the trade as a whole, and reparations remain an active, unresolved subject of political and legal debate in multiple countries.

What Changed Afterward

The abolitionist movements that grew across Britain, the United States and elsewhere from the late 18th century produced some of the first sustained international human-rights advocacy campaigns, including the systematic use of testimony (such as Equiano’s narrative), legal test cases (such as the Zong litigation), and organized public petitioning — methods and precedents that influenced later human-rights and abolitionist movements worldwide, including the eventual abolition of slavery in Brazil (1888), the last country in the Americas to do so.

Sources & Evidence

Last reviewed: January 15, 2025. Found an error? See our corrections policy.