Slavery was legal in roughly half of the states up until the Civil War. After the war ended, the Constitution was amended three times to end slavery and ban discrimination against blacks. But discrimination and segregation did not end until the significant Supreme Court cases of the 1950s.
Adopted between 1865 and 1870, the Reconstruction Amendments to the Constitution form the legal basis for the protection of civil rights:
To supplement the Reconstruction Amendments, Congress passed several civil rights laws in the 1860s and 1870s. These laws gave the president the authority to use the military to enforce civil rights for blacks and made it illegal for states to restrict voting along racial lines.
After the federal troops withdrew from the South at the end of Reconstruction in 1877, white southerners quickly took over state governments and openly flouted the recent laws designed to protect the rights of former slaves. Several state governments in the South went so far as to legalize discrimination of blacks; these laws are known as the Jim Crow laws.
Even though the Fifteenth Amendment gave all men the right to vote, the southern states employed a variety of tactics to prevent blacks from voting, including the following:
Several Supreme Court decisions also weakened the civil rights amendments. In Plessy v. Ferguson (1896), the Court held that the state government could segregate public transportation and thus established the separate but equal doctrine: Blacks could be forced into separate accommodations, including theater seats and hotels, as long as the accommodations were equal to those given to whites.