The significance of the Plessy v. Ferguson case in 1896 lies in its establishment of the "separate but equal" doctrine, which legalized racial segregation in public facilities across the United States. Homer Plessy, a mixed-race man, challenged Louisiana's segregation laws, arguing that they violated his rights under the 14th Amendment. However, the Supreme Court upheld state laws permitting segregation, ruling that the two races could be treated separately as long as facilities were equal. This decision provided legal justification for Jim Crow laws and entrenched systemic racial discrimination for decades, affecting civil rights movements and legal challenges until its eventual reversal in Brown v. Board of Education in 1954.