The expansion of Islam into Africa during the post-classical era had enormous effects in the region. Trade across the Saharan intensified as technology improved, which facilitated the spread of Islam, gold, ivory, salt, and slaves across the continent and Eurasia. In West Africa, the Mali and Songhai Empires became incredibly powerful and wealthy under strong leaders like Mansa Musa. On the eastern coast, Swahili city-states built enormous wealth as they connected the trade across Africa to the Indian Ocean network.