In the ancient city of Taghaza, salt was cut into 200-pound blocks and stored 10 feet underground until it was ready to be transported to market, then the blocks were loaded onto camels and shipped to Timbuktu and the rest of West Africa. Salt was traded for gold at the headwaters of the Niger River where local merchants shipped the blocks downriver.
Salt mining dates back to at least 300 A.D., when camel caravans carried salt out of the Sahara Desert. Camels carried two blocks each, a total of 400 pounds, for 14 days to Timbuktu. West African kingdoms in present-day Nigeria, Mali and Ghana became prosperous with the salt trade.
Mines were controlled by kings, and workers dug in the mines solely for the owner's profit. Everything had to be imported because food was scarce in harsh desert conditions. Buildings in the area were made of the salt blocks themselves because the substance was so readily available. Salt was mined from underneath huge sand dunes that permeate the landscape of the area.
According to National Geographic, camels still made the journey as late as 2003 until vehicular transport began to take over from traditional methods. Caravans often numbered 100 animals that trekked 500 miles through the Sahara north of Timbuktu, in modern-day Mali.