West africa has three major kingdoms: mali; ghana; and songhai. how did the kingdoms, especially ghana, become wealthy?

“Ghana was in an ideal position to become a trading center. To the north lay the vast Sahara, the source of much of the salt. Ghana itself was rich in gold.People wanted gold for its beauty, but they needed salt in their diets to survive. Salt, which could be used to preserve food, also made bland food tasty. These qualities made salt very valuable. In fact, Africans sometimes cut up slabs of salt and used the pieces as money. As trade in gold and salt increased, Ghana’s rulers gained power. Eventually, they built up armies equipped with iron weapons that were superior to the weapons of nearby people. Over time, Ghana took control of trade from merchants. Merchants from the north and south then met to exchange goods in Ghana. By 800 Ghana was firmly in control of West Africa’s trade routes. Nearly all trade between northern and southern Africa passed through Ghana. With so many trespassing through their lands, Ghana’s rulers looked for ways to make money from them. One way they raised money was by forcing traders to pay taxes.Every trader who entered Ghana had to pay a special tax on the goods he carried. Then he had to pay another tax on any goods he took with him when he left. Ghana’s rulers gained incredible wealth from trade, taxes on traders and on the people of Ghana, and their own personal stores of gold. They used their wealth to build an army and an empire.”