Final answer:
Gold and salt were the two primary commodities essential to the economic growth of West African kingdoms like Ghana and Mali, fostering wealth and power through trade.
Step-by-step explanation:
The two commodities most significant to the economic development of West African kingdoms such as Ghana and Mali are gold and salt. These kingdoms flourished due to the control of trade routes and the trade of these precious resources. Gold was especially valuable as it represented wealth and power, becoming a primary export along the trans-Saharan trade routes. Salt, essential for preserving food and maintaining human health, was also highly valued and was used as a form of currency for external trade. Other goods, such as enslaved people, kola nuts, ivory, and textiles were also traded, but gold and salt were the principal goods that contributed significantly to the prosperity of these empires.