The former Western State of Nigeria was formed in 1967 when the Western Region was subdivided into the states of Lagos and Western State. Its capital was Ibadan, which was the capital of the old region. These states make up majority ethnic Yoruba states.

In 1976, the state was subdivided into three new states, Ogun, Ondo and Oyo. The region now consists of nine states, across three geopolitical zones: Delta, Edo, Ekiti, Kwara, Lagos, Ogun, Ondo, Osun, and Oyo States.

Oyo State is the largest state by area in the South West. It covers an area of 28,454km2.^[1]

Lagos State is the most populated state with over 20 million people residing therein.^[1]