Arab and Persian sailors had known about the East African coast for centuries. The monsoon winds made the journey almost effortless. By the first century AD, trading settlements were beginning to appear along Kenya's coast. Merchants arrived with cloth, beads and porcelain. They left with ivory, gold, mangrove poles and enslaved people. The Swahili coast was becoming the busiest marketplace in the Indian Ocean world, and at its heart was a strip of land that would one day be called Kenya.