From the 1500's to 19th century, European ethnocentrists, who deemed themselves the pinnacle of "progress",  often used the term civilize to differentiate themselves from other groups, which they, they characterized as primative or crude. 

So, when they defined the term civlization, they added writing as a requirement despite rather or not a reasonable culture existed.  As a matter of fact, you can search  Webster Dictionary and STILL see the cultural biasness being used.

Nevertheless, West Africa played an active role in trading and grown quite wealthy.  These West African civilizations which provided the world gold included the Ghana, Mali, Songhay, Moroccan empires plus the  Kanem Empire (700?-1890). There were other kingdoms and empires that existed such as Nok, Karnem, Bornu, Hausa, Ashante, Ibo, Dahomey, Sanegambia, Benin, and Yoruba.

Tenkamenin King of Ghana (1037 - 1075 A.D.)--
The king who's strength was in government.  Each day he went out and listen to the concerns of the people. Democratic monarchy and religious tolerance.  Also when Ghana was in it's highest stage economically.

Mali's momumental moment of glory occurred around early 14th century when it was known for it's prosperity and peace as well as law, order, and justice.  In 1326 AD, Mansa Kankan Musa emerged as a powerful king who extended the Mali empire across Africa, and increaased commerce.   Unfortunately the empire began to declined after his death in 1337.

Three years after the civil war,   Askia the Great ruled the empire of Songhay. He very much emulated Mansa Musa by adopting Islam. Timbuktu was the cultural capital as well as the center of international commerce.  Even the Portuguese established trading with them in the year 1448. Unfortunately, the Songhay Empire went into turmoil in 1591 when the Moors invaded.  And when the Moors left, Europeans seized colonial power of the land.