Final answer:
The Plessy v. Ferguson decision in 1896 entrenched de jure segregation by establishing the "separate but equal" doctrine, which led to inferior facilities for African Americans and legitimized discrimination until it was overturned by the Brown v. Board of Education ruling in 1954.
Step-by-step explanation:
In 1896, the Supreme Court case Plessy v. Ferguson established the "separate but equal" doctrine. This doctrine had a profound and detrimental impact on minorities, specifically African Americans, by legitimizing de jure segregation. It legally sanctioned the separation of races in public accommodations and led to the widespread implementation of the Jim Crow laws across the United States, predominantly in the South. Although the ruling mandated that the separate facilities for whites and non-whites be equal, the reality was far from it.
Facilities for African Americans were almost always of much lower quality, thus entrenching a societal structure that was distinctly unequal and discriminatory. This legal precedent stood unchallenged until the pivotal 1954 Supreme Court case of Brown v. Board of Education, which overturned the "separate but equal" principle by declaring that segregated educational facilities are inherently unequal, leading to the end of de jure segregation in public schools.