Era of the slave trade
The flag of the
, a Portuguese company that traded in several commodities and slaves around the Guinea coast from the 15th century
The Portuguese Crown commissioned its navigators to explore the Atlantic coast of West Africa to find the sources of gold. The gold trade was controlled by
Morocco, and Muslim caravan routes across the Sahara also carried salt, kola, textiles, fish, grain, and slaves.
 The navigators first passed the obstruction of
Cape Bojador in 1437 and were able to explore the West African coast as far as
Sierra Leone by 1460 and colonize the
Cape Verde islands from 1456.
The gold ultimately came from the upper reaches of the
Niger River and
Volta River and the Portuguese crown aimed to divert the gold trade towards the coast. To control this trade, the king ordered the building of a castle, called São Jorge da Mina (now
Elmina Castle), on the
Portuguese Gold Coast in 1482 and other trading posts. The Portuguese government instituted the
Company of Guinea to deal with the trading and to fix the prices of the goods.
 Besides gold, ivory,
Melegueta pepper and slaves were traded. It is estimated that the Atlantic slave trade transported around 11 million people from Africa between 1440 and 1870, including 2 million from Senegambia or
This area was the source of an estimated 150,000 African slaves transported by the Portuguese, mainly from Upper Guinea before 1500, some used to grow cotton and indigo in the previously uninhabited Cape Verde islands.
 Portuguese traders and exiled criminals penetrated the rivers and creeks of Upper Guinea forming a
mulatto population using Portuguese-based
Creole language as their
lingua franca. However, after 1500 the main area of Portuguese interest, both for gold and slaves, was further south in the Gold Coast.
At the start of the 17th century, the main Portuguese bases for the export of slaves were
Santiago, Cape Verde for the Upper Guinea traffic, and
São Tomé Island for the
Gulf of Guinea. In the 1630s and 1640s, the Dutch drove the Portuguese from most of the Gold Coast, but they retained a foothold at São João de Ajuda, now called
Benin, as they preferred to acquire slaves from the Gulf of Guinea rather than Upper Guinea before the 1750s. In the 17th century, the French at
Saint-Louis, Senegal, the English at
Kunta Kinteh Island on the
Gambia River and Dutch at
Gorée had established bases in Upper Guinea.
The very weak Portuguese position in Upper Guinea was strengthened by the first
Marquess of Pombal who promoted the supply of slaves from this area to the provinces of
Maranhão in northern
Brazil, and between 1757 and 1777, over 25,000 slaves were transported from the “Rivers of Guinea”, which approximates Portuguese Guinea and parts of
Senegal, although this area had been largely neglected by the Portuguese for the previous 200 years.
Bissau, founded in 1765, became the centre of Portuguese control.
Further British interest in the area led to a brief attempt in the 1790s to establish a base on the island of
Bolama, where there was no evidence of any continuous Portuguese presence. Between the retreat of the British settlers in 1793 and the official Portuguese occupation of the island in 1837 there were several attempts to establish a European presence on the island. Even after the Portuguese had asserted their claim in 1837, Afro-Portuguese lived and worked there alongside Afro-British from Sierra Leone, since Britain did not relinquish its claim to Bolama until 1870.
The abolition of the slave trade by Britain in 1807 presented the slave traders of Guinea with a virtual monopoly of the West Africa slave trade with Brazil. Despite the Brazilian and Portuguese governments agreeing to stop this traffic in the 1830s, it probably continued at 18th-century levels, and only declined significantly after 1850, when the British government put pressure on Brazil to enforce its existing ban on the import of slaves. The last significant consignment of West African slaves reached Brazil in 1852.