Final answer:
Traders crossed the Sahara Desert primarily to trade for gold dust with the state of Ghana, facilitated by camel caravans and linked to the growth of Islam and West African empires.
Step-by-step explanation:
Caravan traders traveled across the Sahara Desert primarily to trade for gold dust in the state of Ghana. During the ninth to the fifteenth centuries CE, camel caravans became a vital link between West Africa and the Mediterranean world, facilitating the movement of goods including salt, ivory, and gold. The emergence of powerful West African kingdoms like the Mali Empire and the influence of Islam greatly expanded these trans-Saharan trade networks. Gold, sourced predominantly from the region of present-day Ghana, was traded northward and became a significant commodity influencing global economies and trade systems of the medieval period.