Niger
Several important empires developed in the upper Niger Basin, starting with the Kingdom of Ghana by the 5th century AD. Following Ghana's demise around 1200, the Mali Empire rose to prominence. The decline of Mali in the 15th century coincided with the rise of Songhai, centered at Gao. In the mid-19th century the Mandingo state headed by Samory Touré and the Tukolor Empire of Umar al-Hajj arose in the upper Niger Basin; both were conquered by the French at the end of the century.
In Nigeria, major empires such as Ife, Oyo, Benin, and Sokoto extended their influence over parts of the Niger Valley at various times. The Nupe kingdom, centered at Bida, and the Borgu kingdom at Bussa had established themselves in the Niger Valley by the 15th century. Several city-states in the Niger Delta, most notably Brass and Bonny, prospered through their participation in trade with Europeans, exporting slaves, ivory, and palm oil.
Europeans had long known that a massive river flowed through the West African savanna, but its course remained a mystery. Some hypothesized it flowed west, emptying via the Sénégal and Gambia rivers into the Atlantic. The expedition of Scottish explorer Mungo Park from 1795 to 1798 proved the Niger flowed eastward, but whether it emptied into the Nile, the Congo, an inland lake, or the Gulf of Guinea was still unknown. The Niger mystery was finally solved through expeditions headed by Scottish explorer Hugh Clapperton from 1823 to 1825 and by British explorer Richard Lemon Lander in 1830. French explorers, most importantly René-Auguste Caillié, also visited parts of the upper and middle Niger during the 19th century.
Throughout the 19th century the British government, often collaborating with trading companies, solidified its control over the Niger delta and the Nigerian coast. By 1900 most of present-day Nigeria had been occupied. The Niger and Benue rivers provided access to the interior, which the British exploited for commercial, military, and political purposes. Upstream from Nigeria, the rest of the Niger Basin was within the colony of French West Africa. Except for Guinea, which became independent from France in 1958, colonial rule throughout the region ended in 1960.