Plessy v. Ferguson
Homer Plessy, a 30-year-old black man who lived in Louisiana, was arrested for sitting in the White Only car of the East Louisiana Railroad. He went to court, saying that the law that allowed for separate cars for black people and white people violated the fourteenth amendment (which provides for equal protection under the law). The case worked its way from the local level all the way up to the Supreme Court.
Each court, including the Supreme Court, found Plessy guilty of not leaving the white car. The majority opinion stated that "A statute which implies merely a legal distinction between the white and colored races -- a distinction which is founded in the color of the two races, and which must always exist so long as white men are distinguished from the other race by color -- has no tendency to destroy the legal equality of the two races..." This came to be known as the "separate but equal" doctrine.