Final answer:
The decision in Plessy v. Ferguson was crucial as it solidified the 'separate but equal' doctrine, which permitted legalized racial segregation, affecting African Americans for decades until it was overturned by Brown v. Board of Education.
Step-by-step explanation:
The Supreme Court's decision in the case of Plessy v. Ferguson was important because it permitted legalized racial segregation for many years. The 1896 ruling established the 'separate but equal' doctrine, legitimizing segregation under the premise that separate facilities for different races were acceptable if they were equivalent. This doctrine validated the system of Jim Crow laws that enforced racial segregation in the southern United States. However, this ruling was eventually overturned by the landmark Supreme Court case Brown v. Board of Education in 1954, which declared that 'separate educational facilities are inherently unequal' and began the process of desegregation.