Final answer:
De jure segregation in the South legally enforced racial separation and discrimination against African Americans through Jim Crow laws, leading to inferior public facilities and societal inequality until the Brown v. Board of Education case began to overturn such laws.
Step-by-step explanation:
De jure segregation affected African Americans in the South by enforcing legal racial separation and discrimination. This type of segregation meant that segregation was embedded in the law, requiring separate facilities for Blacks and Whites in public places like schools, transport, and restaurants. These laws, known as Jim Crow laws, were upheld by the Plessy v. Ferguson Supreme Court decision, which declared 'separate but equal' facilities constitutional. This led to inferior services for African Americans and reinforced a caste-like system in Southern society. It wasn't until the landmark Brown v. Board of Education case in 1954 that the Supreme Court overturned this doctrine, setting the stage for the Civil Rights Movement which fought to end such institutionalized racism.