The Songhai Empire (also transliterated as Songhay) was a state that dominated the western Sahel in the 15th and 16th century. At its peak, it was one of the largest states in African history. The state is known by its historiographical name, derived from its leading ethnic group and ruling elite, the Songhai. Sonni Ali established Gao as the capital of the empire, although a Songhai state had existed in and around Gao since the 11th century. Other important cities in the empire were Timbuktu and Djenné, conquered in 1468 and 1475 respectively, where urban-centered trade flourished. Initially, the empire was ruled by the Sonni dynasty (c.–1493), but it was later replaced by the Askia dynasty (1493–1591).