In 1892, Homer Plessy - who was seven-eighths Caucasian - took a seat in a "whites only" car of a Louisiana train.  He was arrested after he refused to move to the car reserved for blacks.  On appeal, the U.S. Supreme Court upheld state-imposed racial segregation, relying on the "separate but equal" doctrine: Separate facilities for blacks and whites satisfied the Fourteenth Amendment so long as they were equal.