The "Separate But Equal" doctrine was a legal principle in the United States that allowed for racial segregation under the guise of equal facilities and services for both Black and white individuals. This doctrine was established by the Supreme Court in the landmark case of Plessy v. Ferguson in 1896.

The case involved Homer Plessy, a Black man who was arrested for refusing to leave a whites-only train car in Louisiana. The Supreme Court upheld the state law mandating racial segregation on trains, ruling that as long as facilities for Black and white people were deemed "separate but equal," segregation was constitutional.

However, in reality, the facilities provided for Black individuals were almost always inferior to those for white individuals, leading to significant disparities in resources, opportunities, and quality of life. This doctrine further entrenched racial discrimination and reinforced the second-class citizenship of Black Americans.

The "Separate But Equal" doctrine was finally overturned by the Supreme Court in the case of Brown v. Board of Education in 1954, which declared that separate educational facilities were inherently unequal and violated the 14th Amendment's equal protection clause. This decision marked a pivotal moment in the civil rights movement and began the process of dismantling legalized segregation in the United States.