Dead civs owning my cities?

[freedomna]

I am currently playing as America and I was fighting a war against the Congo. I managed to capture all of their cities (thus killing the civ) yet next to the cities I captured it still says "(Congo)". Is there anyway to remove this?

 

[Hydromancerx]

This is an assimilation feature. Which mean its producing African culture in that city. As opposed to cities you found which are North American culture. Thus allowing you to unlock both African and North American based culture wonders.