Plessy v. Ferguson, 163 U.S. 537 (1896), is number 12 on the list of most cited US Supreme Court decisions.
The 7 to 1 ruling upheld state-imposed racial segregation. The Court ruled that separate facilities for blacks and whites satisfied the Fourteenth Amendment requirement of equal protection. Plessy was overturned by Brown v. Board of Education in 1954. The Brown decision is the most cited Supreme Court decision.
The e-book contains the text of both opinions.