Answer:
European sailors first reached sub-Saharan Africa in 1442, when Portuguese ships reached the Senegal river. The Portuguese had been sailing the coasts of Morocco and Western Sahara since 1413, when they captured the Moroccan city of Ceuta [still a Spanish city today]. Between 1413 and the 1440s, the Portuguese established several fortified settlements along the Moroccan coast, especially at Arzila, Mogador (now Essaouira), Safi, and Tangier; they retained a strong presence in Morocco until 1578, when the Portuguese King Sebastião I and much of the Portuguese nobility were killed at the Battle of Alcácer-Quibir. By 1471, West African leaders between the coasts of Senegal and Ghana had established commercial and diplomatic connections with Portuguese traders [major early sites of trade and settlement were on the Gambia river, Bugendo on the São Domingos river in Guinea-Bissau, and Sierra Leone].
Step-by-step explanation:
For the next 150 years, West African rulers and traders came across the Portuguese more than any other European nation. [There were also smaller trading missions led by the English and the French, but these were less frequent]. In the beginning, the Portuguese main motivations were: 1, an interest in the extensive gold production of Bono-Mansu and the Akan states; 2, competition with the Ottoman Empire to access this gold [the Ottomans had captured Constantinople in 1453, prompting a crisis in Christian Europe]; 3, the desire to find a trade route to markets in India around the Cape of Good Hope; 4, ever increasingly, the trade in enslaved persons.
By the 1590s, the Dutch began to rival the Portuguese as the major European trading nation in Africa. Their ships were bigger and better, and the goods they traded with African political leaders were of much higher quality. The Dutch had captured many of the main Portuguese trading stations in West Africa by 1650, especially at Gorée in Senegal (in 1621), at Elmina in Ghana (in 1637), and at Luanda in Angola (in 1641). Initially the Dutch were mainly interested in textiles, animal hides [for the leather industry], and ivory, but by the middle of the 17th century they too turned to slave trading. The Dutch interest in slave trading dates to the 1620s and the capture of half of the Brazilian colonies from the Portuguese. From 1630 to 1654 the Dutch controlled the northern part of Brazil, and the associated sugar plantations which used the labour of enslaved persons; their growing colonial interests drove their interest in slave trading, which took over in the second half of the 18th century.