structural:scholar_edition, linguistic:translation, quality:correction, quality:corruption
Osun State, occasionally known as the State of Osun by the state government, is a state in southwestern Nigeria; bounded to the east by Ekiti and Ondo states for 84 km and for 78 km respectively, to the north by Kwara State for 73 km, to the south by Ogun State for 84 km and to the west by Oyo State, mostly across the River Osun. Named for the River Osun—a vital river which flows through the state—the state was formed from the southeast of Oyo State on 27 August 1991 and has its capital as the city of Osogbo. Of the 36 states of Nigeria, Osun is the ninth smallest in area and 25th most populous state with an estimated population of about 4.7 million as of 2016. Geographically, the state is divided between the Nigerian lowland forests in most of the state and the drier Guinean forest–savanna mosaic in the north. The major geographical features are rivers including the state's namesake, the River Osun which bisects the state's interior before forming much of the state's southwestern border with Oyo State and flowing south. Other important rivers are the Erinle and Oba rivers, both Osun tributaries which flow from the north before meeting the Osun along the southwestern border. Among the state's fauna are mona monkey, common kestrel, purple heron, and royal antelope, along with some of Nigeria's last remaining Nigeria-Cameroon chimpanzee and African forest elephant which inhabit the heavily threatened forests along the southern borders with Ondo and Ogun states. Osun State is primarily inhabited by the Yoruba people, mainly of the Ibolo, Ifẹ, Igbomina, Ijesha, and Oyo subgroups. In the pre-colonial period, the area that is now Osun State was split up between various Western Yoruba states with some states being town-based as others were part of larger empires like the Oyo Empire. From 1877 to 1893, Western Yoruba states fought the Kiriji War alongside other Eastern Yoruba groups against Eastern Yoruba groups; the war ended in a British-brokered stalemate before the area was colonized and incorporated into the British Southern Nigeria Protectorate which later merged into British Nigeria in 1914. After independence in 1960, the area of now-Osun was a part of the post-independence Western Region until 1967 when the region was split and the area became part of the Western State. In 1976, the Western State was split and the state's west became Oyo State. Fifteen years later, Oyo State's east was broken off to form Osun State. Economically, Osun State is largely based around agriculture, mainly of cocoa, cassava, millet, maize, potato and yam crops. Other key industries are services, especially in urban areas, along with artisanal mining and livestock herding. Osun is home to several of Nigeria's most famous landmarks, including the campus of Obafemi Awolowo University, one of Nigeria's pre-eminent institutions of higher learning. The university is located in the ancient town of Ile-Ifẹ, an important early center of political and religious development for Yoruba culture. Other important cities and towns include the ancient kingdom-capitals of Ila Orangun, Iragbiji, Ada, Ikirun, Oke-Ila Orangun, Ipetu-Ijesha, Ijebu-Jesa, Erin Oke, Ipetumodu, Ede, Iwo, Ejigbo, Ibokun, Ode-Omu, Otan Ayegbaju, Ifetedo, Esa-Oke, Ilesa, Okuku, Otan-Ile and Igbajo. Osun State is additionally noted for having the second highest literacy rate in the country.