The advent of Portuguese explorers on the Fanti coast in 1471 marked the beginning of European contact with the Gold Coast. Initially Europeans were attracted to the coast of today’s Ghana because of her enormous mineral wealth, which earned it the name of the “Gold Coast”. Within ten years of arrival, the Portuguese had built a castle in Elmina and by 1500 they were already exporting at least 567 kilograms (over half tonne) of gold through Elmina annually. This increased to between 900 and 1400 kilograms, roughly equivalent to 10% of total world supply, by 1600. The French, the English, the Dutch, the Swedes, the Danes and the Brandenburghers of the Prussians soon followed the Portuguese. All of these European nations built forts, lodges and castles along the Gold Coast littoral to establish their presence and to participate in the lucrative gold trade. One such fort, with an interesting history not least because it had a Gold Coast governor in the 17th century, was the Swedish headquarters in Osu. Now known as Christainborg Castle, it was taken over by the Danes in 1657 when they drove out the Swedes; it was then enlarged and re-named Christianborg. Thirty-six years later, in 1693, the Akwamu trader and confidant of the Akwamuhene, Asameni, seized it in the name of Akwamuhene from the Danes, and remained there as governor and trader until the Danes were constrained to pay a fee of about 50 gold marks (£1.600) for its return. The 17th century saw a shift of emphasis from the gold trade to the slave trade, as a result of the high demand for labour for the plantations of the New World. The large-scale importation of firearms from the mid 17th century and the resultant increase in the incidence of wars in the Gold Coast hinterland produced millions of captives for transportation to the West Indies and the Americas. The consequences were far reaching gold production virtually ceased leading to a reverse demand from the New World; famine occured in areas before food had been plentiful; while the pace of political centralization increased in those states that benefited from the slave trade. By the turn of the 18th century there already existed in the interior powerful states like Denkyra, Adansi Akyem and Akwamu which was later joined by Asante, and other Akan states and the Ewe and Ga-Adamgbe states. In Northern Ghana the Mole-Dagbani states and Gonja had also attained a high level of centralization. Between 1600 and 1874 when the British converted their forts and settlements along the Gold Coast littoral into a Crown Colony there was further intensification of state building activities in the Gold Coast resulting in the establishment and consolidation of the Ga, the Akwamu, the Akyem, the Asante, the Ewe, the Dagomba and the Gonja. These states and many others were to play prominent roles in the history of the Gold Coast.