São Tomé settlers granted privilege to trade in the "slave rivers"

The pioneer settlers of São Tomé were granted in 1485 a privilege permitting them to trade in the "five slave rivers" — the waterways of the Niger Delta — except in commodities reserved exclusively to the Portuguese crown. This colonisation project initially came to nothing, but a similar privilege was given to the settlers who did occupy the island in 1493. By the following year they had begun to send their ships to the rivers in search of slaves, inaugurating a commerce that continued with little interruption until well into the nineteenth century.