What were Jim Crow laws, and how did "separate but equal" become the law?

Jim Crow laws were state and local laws in the American South, from the late 19th century to the mid-20th century, that forced Black and white people apart in public life. "Separate but equal" became the legal justification when the Supreme Court ruled in 1896, in Plessy v. Ferguson, that segregation did not break the Constitution as long as the separate facilities were equal in quality.

The system grew out of what came after the Civil War. After the last federal troops left the South in 1877, white Democrats held power in every Southern state, and their governments wrote segregation into law. Between 1890 and 1910 ten of the eleven former Confederate states rewrote their constitutions to keep most Black citizens from voting, with poll taxes, literacy tests and record-keeping rules. In Louisiana, only 730 Black voters were still registered in 1910, in a state where, ten years earlier, Black people had made up the majority of the population.

The word "equal" turned out to be an empty promise. Facilities for African Americans were consistently inferior and underfunded, and sometimes did not exist at all. Plessy's own case was staged on purpose: a New Orleans citizens' group persuaded Homer Plessy to test the law, and he took a seat in a whites-only train car in 1892 and refused to leave, so that the law could be tested in court. Only one justice, John Marshall Harlan, sided with him, writing that the Constitution "is color-blind".

Plessy is now widely regarded as one of the worst decisions in the Court's history. It stood for 58 years, and most of what remained of Jim Crow was finally overturned by the Civil Rights Act of 1964 and the Voting Rights Act of 1965.