Excerpts from Books and Wikipedia
"Between the chain of North Africa’s coastal states and the southern margins of the Sahara lies an east-west tier of five states, all but one of them landlocked, dominated by the world’s greatest desert, sustained by modest ribbons of water, and thoroughly under the sway of Islam: Mauritania, Mali, Niger, Burkina Faso, and Chad (Fig. 6-12). Although their huge overall territory is sparsely populated (Fig. 6-2), the populations of these countries total just over 76 million, not insignificant by African standards." [Geography: Realms, Regions, and Concepts, 17th Edition, p. 273]