Africa and the Slave Trade

enslaved africans

The discovery of the Americas created new economic opportunities with agriculture the foundation of these opportunities. In 1493, only a year after his first voyage, Christopher Columbus introduced sugarcane into the Caribbean, the crop on which Europeans built the first plantations in the New World.

Sugarcane demanded a large labor force, particularly at harvest. Europeans sought to meet the demand for labor by using criminals, orphans, indentured servants, and Native Americans.

But there was still a need for laborers. Native Americans succumbed to Old World diseases, and the supply of European laborers met only a fraction of the demand. In the mid-15th century, the Portuguese addressed the problem of labor by enslaving Africans to grow sugarcane on the Madeira Islands in the Atlantic Ocean.


The Spanish used slavery in their New World colony Hispaniola (now the island of Haiti and the Dominican Republic), importing the first slaves in 1502. The institutionalization of slavery in the New World spurred trade in slaves. The fact that demand for slaves outpaced the growth in supply by natural increase nearly everywhere in the Americas perpetuated the slave trade over four centuries.

Portugal Leads Slave Trade

Portugal monopolized the trade at the outset. The Treaty of Tordesillas in 1494 granted Portugal access to Africa and with it, slaves. After 1528, Portuguese shipping companies supplied Spain with slaves through a series of asientos, or contracts.

An asiento specified the delivery of slaves in piezas de India, which quantified labor rather than slaves. Men tallied more piezas than women because of the expectation that men would yield more labor than women. For the same reason, the young were worth more than the old.

Shipping slaves

A cargo of 100 piezas constituted the smallest number of slaves if all were young males and the largest if all were elderly females. Of course slave traders rarely got the “ideal” of all young men fit for the rigors of the plantation.

Market conditions yielded a mix, with a majority being young men with some women also included, particularly those of childbearing age in hopes of perpetuating the slave population by reproduction. A cargo might also contain the prepubescent and elderly because of their low prices. Their purchase, however, entailed risk because they were susceptible to disease and early death.

The value of labor and therefore of slaves fluctuated over time. In 1693, the records of the Portuguese Cacheau Company reveal that one pieza was worth 1.6 slaves. In 1715, however, records of the South Sea Company of Great Britain reveal that the value of one pieza had declined to 1.04 slaves. These figures imply an increase in the demand for slaves over time. Supply rose to meet demand.


Between 1521 and 1550, Spain imported into its colonies 15,000 slaves, 500 per year on average, and between 1551 and 1595, they brought in 36,300 slaves, amounting to 810 per year on average. The largest importer of slaves, Brazil, imported more than 200,000 during these years.

In total Portugal had shipped 264,000 slaves to the New World by 1600. Portugal so dominated trade that by 1600, its maritime rival Britain had shipped only 2,000 slaves to the Americas. No other nation participated in the trade until after 1600.

Portugal’s trade in slaves benefited from political instability in Africa. War engulfed the empire of Jolof, spanning modern Senegal and Gambia, in the middle of the 16th century. Warlords enslaved prisoners, trading them with Portugal for guns.

At the same time, the deterioration of the central government of Kongo, modern Angola, Cabinda, and the Republic of the Congo permitted the Portuguese access to the interior of the kingdom and to a larger number of slaves than had been possible when Kongo confined Portugal to the coast.

Slaves sale

In 1614, Portugal allied with the Jaga, a group hostile to the Ndongo rulers of Angola. The resulting war won Portugal captives it sold as slaves. New alliances after 1640 gave Portugal access to slaves in Luanda, the modern capital of Angola.

Political instability gave Europeans more slaves than they might otherwise have expected, for Africa was impenetrable to Europeans into the 19th century. Tropical diseases made it hazardous for Europeans to roam the interior of the continent in search of slaves. Where African tribes remained united, they kept Europeans at arm’s length.

Instead, Europeans established fortresses along the western coast of Africa, the first at Elmina, a town in Ghana, in 1482, and awaited the delivery of slaves from African merchants and chieftains. Once at the coast, slaves waited in dungeons, pens, or stockades until the arrival of a ship. Both Africans and Europeans, intermingling for the first time, were at risk of disease. Confinement in tight quarters on the coast and aboard ship exacerbated the danger to Africans of an epidemic.

Slave Ship Conditions

Once onboard the ships, slaves endured lengthy waits until the captain had enough slaves and the right force and direction of wind to sail. Seldom less than a month, the wait on the coast sometimes stretched to half a year. All the while slaves, packed 100–1,000 per ship, depending on its size, occupied little more than six square feet of space with two or three feet of headroom. Slavers separated men from women, shackling the men in pairs to reduce the danger of rebellion.

Long chains tethered groups of slaves, kept below deck most of the time, for movement to the deck for fresh air and meals. The duration of the wait on the coast and the voyage to the Americas tempted the all-male crews to rape female slaves.

Once a ship set sail, slaves were vulnerable to the vicissitudes of weather and wind. Rain prevented them from getting fresh air on deck and increased the incidence and spread of diseases. Storms imperiled even the most promising crossing.

In 1738, a storm assailed the Dutch ship Leusdan only days from its destination. When it began to leak, the crew, fearing a fight over the lifeboats, locked some 660 slaves below deck, leaving them to drown. Only the crew and 14 slaves on deck survived. The absence of wind brought ships to a standstill and strained the food supply. Ship captains rarely had more than three months of food at the start of a voyage and reduced slave rations on long trips.

The crossing from the Guinea Coast was especially perilous because ships had to traverse the doldrums twice and thereby risk a lengthy calm. One study estimated the mortality rate for ocean crossings of fewer than 20 days at 8 percent, though the death rate increased to nearly one-quarter for voyages longer than two months. Malaria, yellow fever, and intestinal ailments accounted for two-thirds of deaths, and smallpox, scurvy, and suicide the remaining third.

Once a ship reached its destination, an inspector boarded to check slaves for disease, quarantining all slaves if he found one with a communicable disease and prolonging their stay aboard ship until contagion had passed. On land, slaves at last had fresh food and water.

Traders amassed slaves for sale once ashore, selling the young and old first and holding men and women of childbearing age for sale until last in the expectation that prices would rise with the eagerness of buyers to close the deal.

The fact that ovulating women fetched a higher price than pre- and postmenopausal women contradicts the assertion of slave traders that they did not sell slaves for the purpose of breeding. Traders sold most slaves by auction, though an alternative was to fix the price for a group of slaves of similar age and physical condition and allow buyers to choose from among this group.

Other Nations Enter the Slave Trade

Portugal’s hold on the slave trade began to weaken in the 17th century, as the Netherlands entered the fray. After 1630, the Dutch imported into northern Brazil slaves they wrested from Portugal. Taking Curaçao in 1634, the Dutch used it to funnel slaves to their colonies and to those of Portugal, Spain, Britain, and France.

In 1637, the Netherlands captured the Portuguese fortress at Elmina, making it the point of origin of the Dutch slave trade. After 1667, the Netherlands imported slaves into Suriname. In total the Netherlands brought 39,900 slaves to the New World between 1601 and 1650 with the number rising to 76,400 between 1726 and 1770. Thereafter the Netherlands’s share of the slave trade decreased rapidly.

Britain also contested Portuguese dominance. The spread of tobacco in Virginia after 1617 opened British North America to the slave trade. In 1619, the Dutch landed 20 slaves, the first shipment of its kind, in Jamestown. During much of the 17th century, the slave trade in the thirteen colonies was more trickle than deluge.

In 1640, Virginia had only 150 slaves and in 1670, fewer than 1,000. In contrast to Latin America and the Caribbean, slaves in the thirteen colonies increased their numbers through reproduction, diminishing the need to import slaves.

The slave trade in British North America was strongest after the decline of indentured servitude around 1670 and the rise of rice plantations along the Carolina coast about 1700. The thirteen colonies, according to one estimate, imported between 1619 and 1750, roughly 201,500 slaves, an average of 1,550 per year. By comparison the French imported 1,690 slaves per year on average into the island of Martinique between 1664 and 1735 and the Spanish 3,880 per year on average into its colonies between 1640 and 1750.

Following the pattern of British North America, the colonization of the Caribbean opened it to the slave trade. Settling Barbados in 1624, Britain imported the first slaves in 1627. Thereafter the slave trade grew with the spread of sugar cultivation as the trade had in the thirteen colonies with the tobacco boom.

Barbadian imports increased from 6,500 slaves between 1640 and 1644 (an average of 1,300 per year) to 36,400 between 1698 and 1707 (an average of 3,640 per year). In Jamaica sugar and the slave trade took hold in the middle of the 17th century.

Between 1651 and 1675, planters imported 8,000 slaves, an average of roughly 330 per year, roughly one-sixth the number imported into Barbados. By the turn of the century, however, Jamaica had eclipsed Barbados, importing between 1676 and 1700 77,100 slaves, an average of roughly 3,210 per year.

Extrapolating the number of imports from the Royal African Company, a slave trading firm granted a monopoly by King Charles II, to all traders throughout Jamaica, planters imported into the island roughly 7,800 slaves between 1708 and 1711, an average of 2,600 per year.

Between 1655 and 1674, Barbados supplied Jamaica with one-third of its slaves though the proportion fell by the turn of the 18th century to 5 percent. By then most imports came from Africa though the voyage to Jamaica was 1,000 miles farther west than Barbados. The Leeward Islands were the last of Britain’s Caribbean holdings to enter the slave trade. By 1670, island planters had imported only 7,000 slaves.

The numbers grew to 44,800 between 1672 and 1706, an average of 1,280 per year, with another 43,100 between 1707 and 1733, an average of 1,600 per year. In total the British imported 250,000 slaves into the Caribbean by 1700, and throughout the Americas, traders of all nations bought and sold 266,100 slaves between 1519 and 1600.

This represents an average of 3,300 per year, with the number rising to roughly 1.3 million between 1726 and 1750, an astonishing average of 52,000 per year. In all the New World absorbed more than 1.5 million slaves between 1519 and 1750.