History of Africa usually governed by an "oba" and an "iwarefa", a council of chiefs who advised the "oba." by the 18th century, the Yoruba city-states formed a loose confederation, with the "Oni" of Ife as the head and Ife as the capital. As time went on, the individual city-states became more powerful with their "obas" assuming more powerful spiritual positions and diluting the authority of the "Oni" of Ife. Rivalry became intense among the city-states. The Oyo Empire rose in the 16th century. The Oyo state had been conquered in 1550 by the kingdom of Nupe, which was in possession of cavalry,
Oyo Empire in the present Oyo died in 1905. See List of rulers of the Yoruba state of Oyo. During the colonial period, the Yorubas were one of the most urbanized (living in city-like areas) groups in Africa. About 22% of the population lived in large areas with population exceeding 100,000 and over 50% lived in cities made up of 25,000 or more people. The index of urbanization in 1950 was close to that of the United States, excluding Ilorin. The Yoruba continue to be the most urbanized African ethnic group today. Old Oyo linked cities such as Ibadan, Osogbo, and Ogbomoso,