A typical sign seen during the Jim Crow era denoting segregated drinking fountains.
If it may be said of the slavery era that the white man took the world and gave the Negro Jesus, then it may be said of the Reconstruction era that the southern aristocracy took the world and gave the poor white man Jim Crow. He gave him Jim Crow. And when his wrinkled stomach cried out for the food that his empty pockets could not provide, he ate Jim Crow, a psychological bird that told him that no matter how bad off he was, at least he was a white man, better than the black man. And he ate Jim Crow. And when his undernourished children cried out for the necessities that his low wages could not provide, he showed them the Jim Crow signs on the buses and in the stores, on the streets and in the public buildings. And his children, too, learned to feed upon Jim Crow, their last outpost of psychological oblivion. Thus, the threat of the free exercise of the ballot by the Negro and the white masses alike resulted in the establishment of a segregated society.
~ Martin Luther King Jr. in his "How Long, Not Long" speech.

The Jim Crow laws were state and local laws enforcing racial segregation in the Southern United States, largely arising in the immediate aftermath of the end of slavery after the American Civil War. The Jim Crow era is considered to be the peak of white supremacy and anti-black racism in the United States.

Other areas of the United States were affected by formal and informal policies of segregation as well, but many states outside the South had adopted laws, beginning in the late 19th century, banning discrimination in public accommodations and voting. Southern laws were enacted in the late 19th and early 20th centuries by white Southern Democrat-dominated state legislatures to disenfranchise and remove political and economic gains made by African Americans during the Reconstruction period. Jim Crow laws were enforced until 1965.

In practice, Jim Crow laws mandated racial segregation in all public facilities in the states of the former Confederate States of America and in some others, beginning in the 1870s. Jim Crow laws were upheld in 1896 in the case of Plessy v. Ferguson, in which the Supreme Court laid out its "separate but equal" legal doctrine concerning facilities for African Americans. Moreover, public education had essentially been segregated since its establishment in most of the South after the Civil War.

Although in theory, the "equal" segregation doctrine was extended to public facilities and transportation too, facilities for African Americans were consistently inferior and underfunded compared to facilities for white Americans; sometimes, there were no facilities for the black community at all. Far from equality, as a body of law, Jim Crow institutionalized economic, educational, political and social disadvantages and second class citizenship for most African Americans living in the United States.

After the National Association for the Advancement of Colored People (NAACP) was founded in 1909, it became involved in a sustained public protest and campaigns against the Jim Crow laws, and the so-called "separate but equal" doctrine.

In 1954, segregation of public schools (state-sponsored) was declared unconstitutional by the Supreme Court under Chief Justice Earl Warren in the landmark case Brown v. Board of Education. In some states, it took many years to implement this decision, while the Warren Court continued to rule against Jim Crow legislation in other cases such as Heart of Atlanta Motel, Inc. v. United States (1964).

In general, the remaining Jim Crow laws were overruled by the Civil Rights Act of 1964 and the Voting Rights Act of 1965.

There is evidence that the government of Nazi Germany took inspiration from the Jim Crow laws when writing the Nuremberg Laws that stripped German Jews of their rights, which in turn eventually lead to the Holocaust.