The primary geographical focus for the historical study of Islam in west Africa, until recently, was the western and central Sudan. As the often-cited J. S. Trimingham wrote (1962:7) “The Guinea States in the south lie outside our sphere since they were not in contact with the Sudan states and were uninfluenced by Islam.” Trimingham's conclusion paralleled those of early twentieth-century French and English scholars who dealt with the issue of Islam in west Africa. Paul Marty's voluminous studies, dating from the second decade of this century, dealt with the Islamic and Muslim-influenced traditions of the various peoples of Francophone west Africa. H. R. Palmer, one of the early British writers of this century, concentrated on the northern territories of Nigeria, where Islam has enjoyed a long history.
Two factors explain the focus of these scholars on the western and central Sudan. First, the better known Islamic-influenced kingdoms of Ghana, Mali, Songhai, and Kanem-Bornu were all located in this region. Second, the Islamic states of the western and central Sudan, in particular, presented the greatest problem to both the French and the British during the early periods of the colonial era. Therefore, the focus on this area may have been motivated by the desire of these writers to understand the Islamic factor. Whatever the motivation of writers like Marty, Palmer, and their associates, Trimingham was wrong to conclude that the “the Guinea States” (i.e., the peoples living in the coastal forest belt) were “uninfluenced by Islam.”