Ghana was well placed to take advantage of trade. It was located midway between the desert, the main source of salt, and the goldfields of the upper Senegal River in the savannah woodlands in the south. Camel caravans crossing the Sahara brought goods such as copper and dried fruit, as well as salt that was mined at Taghaza in present-day northern Mali. The caravans also brought clothing and other manufactured goods, which they exchanged for kola nuts, hides, leather goods, ivory, gold, and slaves. Taxes collected on every trade item entering the kingdom were used to pay for government, a huge army which protected the kingdom's borders and trade routes, and the upkeep of the capital city and major markets. However, it was control of the gold fields in the southwest that was essential to Ghana's political control and economic prosperity. The location of these goldfields was kept strictly secret by the Soninke. By the tenth century, Ghana was an immensely rich and prosperous empire, probably controlling an area the size of Texas or Nigeria in what is now eastern Senegal, southwest Mali, and southern Mauritania. The ruler was acclaimed as the "richest king in the world because of his gold" by Arab traveler Ibn Haukal, who visited the region in about 950 A.D. Demand for gold increased in the ninth and tenth centuries for minting into coins by the Islamic states of North Africa. As the trans-Saharan trade in gold expanded, so did the state of Ghana. The trans-Sahara trade also brought Islam to the empire, initially to the rulers and townspeople.
Source: A.R.K Bawku