The correct answer is SEGREGATION.
Segregation is defined as a systematic separation of a population in terms of race or ethnicity in everyday life, for example in public facilities such as in schools or in the public transport.
In the United States, after the enactment of the Reconstruction Amendments that guaranteed equality of rights for all US citizens, many Southern states tried to circumvent such provisions with the enactment of the so-called Jim Crow laws. These legal instruments were based on the "separate but equal lemma" which stated that, if the facilities were equal in quality, the equal rights provision was being respected. Hence, this was the legal base that allowed segregation to occur.