the 3rd century CE. It was succeeded by the Sosso in 1230, the Mali Empire in the 13th century CE, and later by the Songhai and Sokoto Caliphate. There were also a number of forest empires and states in this time period. Following the collapse of the Songhai Empire, a number of smaller states arose across West Africa, including the Bambara Empire of Ségou, the lesser Bambara kingdom of Kaarta, the Fula/Malinké kingdom of Khasso (in present-day Mali's Kayes Region), and the Kénédougou Empire of Sikasso. European traders first became a force in the region in the 15th century. The Atlantic slave trade began, with the Portuguese taking hundreds of captives back to their country for use as slaves; however, it would not begin on a grand scale until Christopher Columbus's voyage to the Americas and the subsequent demand for cheap colonial labour. As the demand for slaves increased, some African rulers sought to supply the demand by constant war against their neighbours, resulting in fresh captives. European, American and Haitian governments passed legislation prohibiting the Atlantic slave trade in the 19th century, though the last country to abolish the institution was Brazil in 1888. In 1725, the cattle-herding Fulanis of Fouta Djallon launched the first major reformist jihad of the region, overthrowing the local animist, Mande-speaking elites and attempting to somewhat democratize their society. At the same time, the Europeans started to travel into the interior of Africa to trade and explore. Mungo Park (1771–1806) made the first serious expedition into the region's interior, tracing the Niger River as far as Timbuktu. French armies followed not long after. In the Scramble for Africa in the 1880s the Europeans started to colonise the inland of West Africa, they had previously mostly controlled trading ports along the coasts and rivers. Following World War II, campaigns for independence sprung up across West Africa, most notably in Ghana under the Pan-Africanist Kwame Nkrumah (1909–1972). After a decade of protests, riots and clashes, French West Africa voted for autonomy in a 1958 referendum, dividing into the states of today; most of the British colonies gained autonomy the following decade. Since independence, West Africa has suffered from the same problems as much of the African continent, particularly dictatorships, political corruption and military coups; it has also seen bloody civil wars. The development of oil and mineral wealth has seen the steady modernization of some countries