Why did the Trade Begin?
Expanding European empires in the New World lacked one major resource -- a work force. In most cases the indigenous peoples had proved unreliable (most of them were dying from diseases brought over from Europe), and Europeans were unsuited to the climate and suffered under tropical diseases. Africans, on the other hand, were excellent workers: they often had experience of agriculture and keeping cattle, they were used to a tropical climate, resistant to tropical diseases, and they could be "worked very hard" on plantations or in mines.
Was Slavery New to Africa?
Africans had been traded as slaves for centuries -- reaching Europe via the Islamic-run, trans-Saharan, trade routes. Slaves obtained from the Muslim dominated North African coast however proved to be too well educated to be trusted and had a tendency to rebellion.
See The Role of Islam in African Slavery for more about Slavery in Africa before the Trans-Atlantic Trade began.
Slavery was also a traditional part of African society -- various states and kingdoms in Africa operated one or more of the following: chattel slavery, debt bondage, forced labor, and serfdom. See Types of Slavery in Africa for more on this topic.
What was the Triangular Trade?
All three stages of the Triangular Trade (named for the rough shape it makes on a map) proved lucrative for merchants.
The first stage of the Triangular Trade involved taking manufactured goods from Europe to Africa: cloth, spirit, tobacco, beads, cowrie shells, metal goods, and guns. The guns were used to help expand empires and obtain more slaves (until they were finally used against European colonizers). These goods were exchanged for African slaves.
The second stage of the Triangular Trade (the middle passage) involved shipping the slaves to the Americas.
The third, and final, stage of the Triangular Trade involved the return to Europe with the produce from the slave-labor plantations: cotton, sugar, tobacco, molasses and rum.
Origin of African Slaves Sold in the Triangular Trade
Slaves for the Trans-Atlantic slave trade were initially sourced in Senegambia and the Windward Coast. Around 1650 the trade moved to west-central Africa (the Kingdom of the Kongo and neighboring Angola).
The transport of slaves from Africa to the Americas forms the middle passage of the triangular trade. Several distinct regions can be identified along the west African coast, these are distinguished by the particular European countries who visited the slave ports, the peoples who were enslaved, and the dominant African society(s) who provided the slaves.
For more on the regions where slaves were sourced see this map.
Who Started the Triangular Trade?
For two hundred years, 1440-1640, Portugal had a monopoly on the export of slaves from Africa. It is notable that they were also the last European country to abolish the institution - although, like France, it still continued to work former slaves as contract laborers, which they called libertos or engagés à temps. It is estimated that during the 4 1/2 centuries of the trans-Atlantic slave trade, Portugal was responsible for transporting over 4.5 million Africans (roughly 40% of the total).
How Did the Europeans Obtain the Slaves?
Between 1450 and the end of the nineteenth century, slaves were obtained from along the west coast of Africa with the full and active co-operation of African kings and merchants. (There were occasional military campaigns organized by Europeans to capture slaves, especially by the Portuguese in what is now Angola, but this accounts for only a small percentage of the total.)
A Multitude of Ethnic Groups
Senegambia includes the Wolof, Mandinka, Sereer and Fula; Upper Gambia has the Temne, Mende, and Kissi; the Windward Coast has the Vai, De, Bassa, and Grebo.
For more how many slaves were sourced from each region see this table.
Who Has the Worst Record for Trading Slaves?
During the eighteenth century, when the slave trade accounted for the transport of a staggering 6 million Africans, Britain was the worst transgressor - responsible for almost 2.5 million. This is a fact often forgotten by those who regularly cite Britain's prime role in the abolition of the slave trade.
Conditions for the Slaves
Slaves were introduced to new diseases and suffered from malnutrition long before they reached the new world. It is suggested that the majority of deaths on the voyage across the Atlantic - the middle passage - occurred during the first couple of weeks and were a result of malnutrition and disease encountered during the forced marches and subsequent interment at slave camps on the coast.
Survival Rate for the Middle Passage
Conditions on the slave ships were terrible, but the estimated death rate of around 13% is lower than the mortality rate for seamen, officers and passengers on the same voyages.
Arrival in the Americas
As a result of the slave trade, five times as many Africans arrived in the Americas than Europeans. Slaves were needed on plantations and for mines and the majority was shipped to Brazil, the Caribbean, and the Spanish Empire. Less than 5% traveled to the Northern American States formally held by the British.
For more on the regions where slaves ended up see this table.