Several African cities that had at least 4.0 million residents were not mapped. All of them started with fewer than 2.0 million residents in 1900. Three of them, al-Qāhirah, Lagos and Kinshasa-Brazzaville had between 10.0 and 19.999 million metropolitan residents in 2012. In all cases the growth was due in part to national population growth and in part to urbanization. And all three were colonial and then national capitals (although al-Qāhirah has a long pre-colonial history). In the case of al-Qāhirah nearby cities also grew and became part of the metropolitan area. By contrast Lagos is a set of local government areas without a common authority and Kinshasa-Brazaaville consists of two cities on opposite sides of a great river. (Miṣr is mapped for other periods--just not this one. Nigeria and Lagos State are not mapped for any period.)
The other cities, the ones that ended between 4.0 and 9.999 million metropolitan residents, are: Johannesburg (Guateng Province), Alger (in its own province), Abidjan (Côte d'Ivoire), Ibadan (Nigeria), Cape Town (Western Cape Province), Luanda (it its own province), Kano (Nigeria), al-Iskandarīyah (Miṣr), Accra (Ghana), Nairobi (Kenya) and Khartūm (it its own province). (Other than Miṣr none of these areas are mapped for any period.)