Trade was a primary factor in the rise and development of the West African kingdoms of Ghana, Mali, and Songhai. In particular, these kingdoms grew wealthy, powerful, and influential because they were able to collect taxes from traders who crossed their territories. Most commerce consisted of salt from the Sahara Desert to the north being traded for gold from the forests to the south. Since it was necessary for merchants to cross these kingdoms to get from source to market, the kingdoms were well-positioned geographically to benefit.

The money collected from these taxes helped to fund large professional armies. These armies made it possible to conquer and subdue neighboring peoples who had their own resources and trade routes. Once these had been conquered, the West African kingdoms had access to even more tax revenue.

There remains some mystery as to how the Kingdom of Ghana first arose. After some time, trade made it stronger. However, its first advantage may have been access to iron weapons. In the 5th or 6th Century, these metal weapons would have given Ghana a military advantage over their neighbors who still used stone and wooden weapons.

The kingdoms of Ghana, Mali, and Songhai also grew powerful through a comprehensive tribute system. Conquered peoples were required to pay large sums to the kings' treasury in the form of monetary and military tribute. By collecting riches and soldiers, these kingdoms were able to increase their power base significantly while keeping their conquered neighbors dependent on them.

Trade had an enormous influence on the emergence of West African kingdoms. You might even make the claim that these were essentially trading empires, built and maintained through the movement of goods and resulting wealth they obtained. In particular, West African kingdoms flourished based on the Trans-Saharan gold and salt trade.

Gold, coveted for its beauty, was a valuable element in the trade. However, salt—valued for its flavor, as well as the ability to preserve good—was of equal importance. The Kingdom of Ghana was ideally situated to take advantage of both resources, being both rich in gold and with convenient access to Saharan salt mines. The kingdoms of Mali and Songhai used a similar model, trading gold and salt back and forth, accumulating power, and extending their influence as they grew.

The slave trade also brought wealth to certain West African kingdoms. Arab Muslim traders first bought and sold slaves in medieval times, exchanging goods such as horses, cloth, and European weapons. When European powers got involved later, the slave trade became even more lucrative for West African kingdoms than salt or gold, even as it gradually eroded the stability of the region.

All trade is based on connection, which these West African kingdoms capitalized upon. Many trade routes crossed the Sahara desert, using camel caravans to reach markets in North Africa and the Middle East. The Kingdom of Mali used access to the mighty Niger river to expand its trade routes. As ever, proximity to rivers and the agricultural richness of the land were essential elements in the success of the West African kingdoms. When the slave trade with Europe grew more important, access to the Atlantic Ocean became valued as well. Geography always plays a role in the rise and fall of civilizations.

Trade was important to the growth of West African Sahelian Kingdoms in the postclassical period, 600-1450 CE. Three examples of centralized West African Kingdoms were (in chronological order) Ghana, Mali, and Songhai. Without a connection to trade networks throughout North Africa, these Kingdoms would not have been as successful.

Many elites in these kingdoms converted to Islam in order to benefit in trading with Muslim merchants and the Islamic world. From the mid 7th century until the mid 13th century, two Islamic Empires (the Umayyads and Abbasids) ruled over much of the Middle East, North Africa, and parts of Southern Spain. Travelers and traders in these regions, notably the Berber nomadic group, traded goods between West African kingdoms and the Islamic Empires. Mali, for example, profited immensely off of the gold and salt trade along the Trans-Saharan trade routes. Malian Kings, notably Mansa Musa, used these trade routes to make the Muslim pilgrimage to Mecca (the hajj) and they spread West African wealth, culture, and power along the way.

Other factors that led to the rise of West African Kingdoms was a need for centralized, powerful states. Previous groups existed in this region, like the Bantu, who were organized as a stateless society. Due to environmental and agricultural problems, the Bantu migrated South. In order to survive in the harsh desert environment of the Sahel and Sahara deserts, stronger, centralized Kingdoms that relied on trade popped up on rivers, like Timbuktu (the Malian capital) on the Niger River. Without a centralized empire, civilization would not have been as successful in West Africa.