A kingdom in Central Africa, established south of the River Congo by 1300 which became one of the most powerful kingdoms in the region. The Kongo people traded over long distances, exploiting iron and salt mines. On Loanda Island they had a monopoly of nzimbu shells, which provided a local currency. It was the first African kingdom after Ethiopia to be converted to Christianity, by Portuguese missionaries in the 16th century. The Portuguese also brought the slave trade, which encouraged civil wars and weakened the Kongo kingdom by the mid-17th century.