How and when states were created in Nigeria

List of Nigeria’s 36 states and the Federal Capital Territory

Abia
Adamawa
Akwa Ibom
Anambra
Bauchi
Bayelsa
Benue
Borno
Cross River
Delta
Ebonyi
Edo
Ekiti
Enugu
Federal Capital Territory, Abuja
Gombe
Imo
Jigawa
Kaduna
Kano
Katsina
Kebbi
Kogi
Kwara
Lagos
Nasarawa
Niger
Ogun
Ondo
Osun
Oyo
Plateau
Rivers
Sokoto
Taraba
Yobe
Zamfara

By the time that Nigeria got independence it was a federation of the three regions, namely:

Western
Eastern
Northern

Later on another region was added, the Mid-Western Region.

The Mid-Western Region was formed from the Western Region in 1966, and Lagos, the capital, was effectively governed as an unofficial fourth region outside the bounds of the Western Region.

This brought the numbr of regions to 4 as follows:

Western
Mid-Western
Western
Northern

Under the short-lived military government of Aguiyi-Ironsi, Nigeria was reorganized under a central government. Following a coup which resulted in Aguiyi-Ironsi’s deposition and assassination, Nigeria was reorganized as a federal country again with three of the regions being divided into newer entities and all first-level subdivisions being renamed as states.

Western Region was divided into:
Lagos (Lagos)
and Western (Ibadan) states.

Eastern Region was divided into:
East-Central (Enugu),
Rivers (Port Harcourt),
and South-Eastern (Calabar) states;

Northern Region was divided into:
Benue-Plateau (Jos),
Kano (Kano),
Kwara (Ilorin),
North-Central (Kaduna),
North-Eastern (Maiduguri),
and North-Western (Sokoto) states

1976 reorganization of Nigeria’s federating units

In 1976, six years after the end of the civil war, the states were further reorganized:

State boundaries and names were also reorganized.

Benue-Plateau state divided into:
Benue (Makurdi)
and Plateau states.

East-Central state divided into:
Anambra
and Imo (Owerri) states.
Federal Capital Territory (Abuja) formed from parts of Niger and Plateau states.

North-Eastern state divided into:
Bauchi (Bauchi),
Borno,
and Gongola (Yola) states.
Niger (Minna) state split from Sokoto.

Western state divided into:
Ogun (Abeokuta),
Ondo (Akure),
and Oyo states

States of Nigeria from 1987-1991

Akwa Ibom state split from Cross River;
Katsina state split from Kaduna

States of Nigeria from 1991-1996

Abia State split from Imo;
Bendel State divided into Delta and Edo;
Enugu State split from Anambra;
Gongola State divided into Adamawa and Taraba;
Jigawa State split from Kano;
Kebbi State split from Sokoto;
Kogi State formed from parts of Benue and Kwara;
Osun State split from Oyo;
Yobe State split from Borno.

States of Nigeria from 1996

Bayelsa State was split from Rivers;
Ebonyi State was formed from parts of Abia and Enugu;
Ekiti State was split from Ondo;
Gombe State was split from Bauchi;
Nasarawa State was split from Plateau;
Zamfara State was split from Sokoto.