The Kingdom of Ghana lasted from somewhere before 500 C.E until the 1200s.
The most important thing that identifies the wealth and power of the ruler of Ghana is that all the gold and salt traders have to go through him first, and then to get out they have to again. He taxes both ways.
The travel across the Sahara desert was so difficult because it was very hot and there was very minimal water.
Salt was important to West African people because they lived in a very hot part of Africa, which means they lose a lot of salt in their sweat, and they used it to keep their food from spoiling to feed their cattle.
The two groups involved in silent bartering were the Wangaran and traders.
Traders were charged in and out of entering, and they became tired of how expensive it was.