In the first decade of the nineteenth century, two unrelated developments that were to have a major influence on virtually all of the area that is now Nigeria ushered in a period of radical change. First, between 1804 and 1808, the Islamic holy war of Usman dan Fodio established the Sokoto Caliphate, which not only expanded to become the largest empire in Africa since the fall of Songhai but also had a profound influence on much of Muslim Africa to the west and to the east (see fig. 4). Second, in 1807 Britain declared the transatlantic slave trade to be illegal, an action that occurred at a time when Britain was responsible for shipping more slaves to the Americas than any other country. Although the transatlantic slave trade did not end until the 1860s, it was gradually replaced by other commodities, especially palm oil; the shift in trade had serious economic and political consequences in the interior, which led to increasing British intervention in the affairs of Yorubaland and the Niger Delta. The rise of the Sokoto Caliphate and the economic and political adjustment in the south strongly shaped the course of the colonial conquest at the end of the nineteenth century.

Figure 4. The Sokoto Caliphate, Mid-Nineteenth Century

Data as of June 1991