The formation of the first 12 states in Nigeria took place in the year 1967.
Before 1967, Nigeria was divided into three regions: Northern, Eastern, and Western regions. Each region was made up of several provinces, and these provinces were further divided into districts.
However, in May 1967, the then military Head of State, General Yakubu Gowon, announced the creation of 12 states in Nigeria, which replaced the previous regional structure. The new states were designed to reflect Nigeria's diverse ethnic, cultural, and linguistic groups and promote national unity.
The 12 states were: Lagos, Western State, Mid-Western State, Eastern State, Benue-Plateau State, North-Eastern State, Kwara State, Kano State, North-Western State, Cross River State, Rivers State, and South-Eastern State (later renamed to Anambra State).
The creation of these states was not without controversy, as some ethnic groups felt they were not adequately represented in the new state boundaries. Nevertheless, the move was seen as an important step towards addressing Nigeria's diverse and complex sociopolitical landscape.
In summary, the formation of the first 12 states in Nigeria took place in 1967, replacing the previous regional structure and reflecting Nigeria's diverse ethnic, cultural, and linguistic groups.