After initiating the European slave trade in Sub-Saharan Africa through its involvement in the African slave trade, Portugal played a decreasing role in it over the next few centuries. Although they were the first Europeans to establish trading settlements in Sub-Saharan Africa, they failed to press home their advantage. Nevertheless, they retained a clear presence in the three regions which received their particular attention during the original age of exploration. The closest of these, on the sea journey from Portugal, was Portuguese Guinea, known also, from its main economic activity, as the Slave Coast. The local African rulers in Guinea, who prospered greatly from the slave trade, had no interest in allowing the Europeans to move any further inland than the fortified coastal settlements where the trading took place. In the 15th century, Portugal's Company of Guinea was one of the first chartered commercial companies established by Europeans in other continents during the Age of Discovery. The Company's task was to deal with the spices and to fix the prices of the goods. The Portuguese presence in Guinea was largely limited to the port of Bissau. For a brief period in the 1790s, the British attempted to establish a rival foothold on an offshore island, at Bolama. By the 19th century, however, the Portuguese were sufficiently secure in Bissau to regard the neighbouring coastline as their own special territory.