States of Nigeria; their capitals, population, land and area in Km²

State	Capital	Population	Area (Km²)
Abia	Umuahia	2,833,999	4,857
Adamawa	Yola	3,168,101	37,957
Akwa Ibom	Uyo	3,920,208	6,788
Anambra	Awka	4,182,032	4,761
Bauchi	Bauchi	4,676,465	48,197
Bayelsa	Yenagoa	1,703,358	9,363
Benue	Makurdi	4,219,244	30,755
Borno	Maiduguri	4,151,193	72,767
Cross River	Calabar	2,888,966	22,112
Delta	Asaba	4,098,391	17,095
Ebonyi	Abakaliki	2,173,501	6,342
Edo	Benin City	3,218,332	19,584
Ekiti	Ado-Ekiti	2,384,212	5,797
Enugu	Enugu	3,257,298	7,560
Federal Capital Territory	Abuja	1,405,201	7,569
Gombe	Gombe	2,353,879	17,428
Imo	Owerri	3,934,899	5,135
Jigawa	Dutse	4,348,649	23,415
Kaduna	Kaduna	6,066,562	44,217
Kano	Kano	9,383,682	20,389
Katsina	Katsina	5,792,578	23,822
Kebbi	Birnin Kebbi	3,238,628	36,320
Kogi	Lokoja	3,278,487	29,063
Kwara	Ilorin	2,371,089	33,792
Lagos	Ikeja	9,013,534	3,475
Nasarawa	Lafia	1,863,275	26,633
Niger	Minna	3,950,249	72,065
Ogun	Abeokuta	3,728,098	16,850
Ondo	Akure	3,441,024	15,019
Osun	Oshogbo	3,423,535	8,585
Oyo	Ibadan	5,591,589	27,036
Plateau	Jos	3,178,712	26,539
Rivers	Port Harcourt	5,185,400	10,361
Sokoto	Sokoto	3,696,999	32,146
Taraba	Jalingo	2,300,736	59,180
Yobe	Damaturu	2,321,591	44,880
Zamfara	Gusau	3,259,846	33,667
Total		140,003,542	911,519

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 number 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
and Western states.

Eastern Region was divided into:
East-Central,
Rivers,
and South-Eastern states;

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

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
and Plateau states.

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

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

Western state divided into:
Ogun,
Ondo,
and Oyo states

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

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

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