[citation needed] The area is approximately 2,496 km2 in geographical size, which is about 8.77% of Oyo State, and consists mostly of rolling savannah with forests situated along the southern border and in isolated patches along river courses such as the Ogun.
[citation needed] The Ibarapa people are said to have migrated into the area, either as dissidents of the Old Oyo empire, during the periods of constant internecine warfare between the different Yoruba states, as well as refugees escaping the transatlantic and trans-Saharan slave raiding business of the day.
Those who favoured the merger said most Ibarapa historically hail from their Egba neighbours, and that they stood a better chance of rapid development in Ogun, which had just Four divisions, unlike Oyo which had a massive Twelve.
The commission later found out that the siting of the local police divisional headquarter in the town of Eruwa was the root cause of the demands, with those on the east favouring a merger with Ogun, while those on the west were satisfied with the status quo.
[citation needed] In the 1960s, Professor PPS Nylander, obstetrician and gynaecologist conducted a series of research into the phenomenon of twinning and multiple birth in Ibarapa district.