Salt and gold....................also, diamonds.........coffee........etc...............

The emergence of the three centralized states at given points in history can be attributed to the coupling of the lucrative gold trade from the Sudan with the salt brought by North African Muslim traders. Ghana was the richest of the three in c. 1150, owing its wealth primarily to the vast gold fields of Buri and Bambak.

The acceptance of Islam by the rulers of Ghana, Mali and Songhay (also spelled Songhey and Songhai) in c. 1000 encouraged trade between the empires and North Africa. The introduction of Islam also instituted more cosmopolitan social structures, such as universities, world religions and, especially, centralized state systems and military forces.

At its peak, the Mali Empire extended across West Africa to the Atlantic Ocean and incorporated an estimated 40 to 50 million people. The administration of such an enormous territory was formidable and relied on the establishment of a government sensitive to the diversity of the land, population and cultures and accepting of the indigenous rulers and their customs. What distinguished the empires of West Africa, particularly Mali and later Songhay, was their ability to centralize political and military power while allowing the local rulers to maintain their identities along side Islam. The imperial powers were located in active commercial centers like Djenne, Timbuktu and Gao.