In 1890, Louisiana passed the Separate Car Act, requiring separate accommodations for Black and white railway passengers. To challenge the law, the Citizens Committee to Test the Constitutionality of the Separate Car Act recruited Homer Plessy, a man who was an octoroon—meaning he possessed one-eighth African ancestry and seven-eighths European ancestry. Under Louisiana's racial code, his one-eighth blood quantum classified him as Black, yet his light complexion allowed him to pass as white.
This specific blood quantum threshold was crucial to the committee's legal strategy. On June 7, 1892, Plessy purchased a first-class ticket on the East Louisiana Railroad and took a seat in a car reserved for white passengers. The railroad company, which opposed the act due to the extra costs of maintaining additional cars, was actually in on the plot and hired a private detective to arrest Plessy specifically for violating the Separate Car Act.
Plessy's lawyers argued that the law violated his Eighth, Thirteenth, and Fourteenth Amendment rights, emphasizing that the arbitrary legal definition of race based on blood quantum stripped citizens of property rights in their reputation. When the case reached the Supreme Court in 1896 as Plessy v. Ferguson, the court ruled 7-1 against Plessy.
Justice Henry Billings Brown wrote that legal distinctions based on race did not violate the Constitution as long as facilities were equal, establishing the infamous separate but equal doctrine that upheld state Jim Crow laws for nearly six decades.