Oyo State is an inland state in south-western Nigeria, with its capital at Ibadan. It was formed in 1976 from the former Western State, and originally included Osun State, which was split off in 1991. Ibadan is the second largest city in Nigeria and the capital of Oyo State. ... 1976 is a leap year starting on Thursday (link will take you to calendar). ... 1991 is a common year starting on Tuesday of the Gregorian calendar. ...