Powerful kingdoms emerged in West Africa due to the trans-Saharan salt-gold trade. The Empire of Ghana grew wealthy from taxing the trade between North and West Africa. The Empire of Mali later invaded Ghana and established control over the salt-gold trade, becoming enormously wealthy under Mansa Musa who went on Hajj to Mecca. His pilgrimage established Mali's wealth and prominence. The trading empires grew rich from controlling the trade routes and taxing the goods that passed through their territories.