Omanis in the pre-Islamic period were already familiar with the coastal regions of East Africa and the islands east of them. In the early Middle Ages, members of Omani royal families and their followers began to emigrate to the region, with some of them founding small princedoms. After approximately 150 years of Portuguese dominance, the Omanis drove the Portuguese out of the coastal areas north of Mozambique, and a period of prosperity began under Omani rule. In a treaty signed in 1822 between the British and the Omani ruler, Sayyid Said, the British ceded supremacy to the Omanis over the coastal areas of East Africa between northern Mozambique and southern Somalia. This led to another period of prosperity under Omani rule, which ended in the so called "Revolution of Zanzibar" in 1964. In this book the author presents for the first time a comprehensive survey of the archaeological evidence of the Islamic period in the coastal areas of Kenya and Tanzania, as well as relevant written sources in African, Oriental and Western languages and provides a synthesis of the two different sets of sources.