“White nationalist, white supremacist, Western civilization—how did that language become offensive?” the Iowa congressman Steve King inquired of a Times reporter last month. After the remark blew up, King explained that by “that language” he was referring to “Western civilization.” He also said that he condemned white nationalism and white supremacy as an “evil and bigoted ideology which saw in its ultimate expression the systematic murder of six million innocent Jewish lives.” (It’s unclear whether King thinks of Jews as nonwhite.)

However, to answer the congressman’s original question: only after a long struggle. Seventeen states had laws banning interracial marriage, which is pretty much the heart of the doctrine of white supremacy, until 1967, when the Supreme Court declared them unconstitutional. From the Compromise of 1877, which ended Reconstruction, to the Civil Rights Act of 1964 and the Voting Rights Act of 1965, American race relations were largely shaped by states that had seceded from the Union in 1861, and the elected leaders of those states almost all spoke the language of white supremacy. They did not use dog whistles. “White Supremacy” was the motto of the Alabama Democratic Party until 1966. Mississippi did not ratify the Thirteenth Amendment, which outlawed slavery, until 1995.

How did this happen? How did white people in a part of the country that was virtually destroyed by war contrive to take political control of their states, install manifestly undemocratic regimes in them, maintain those regimes for nearly a century, and effectively block the national government from addressing racial inequality everywhere else? Part of the answer is that those people had a lot of help. Institutions constitutionally empowered to intervene twisted themselves every which way to explain why, in this matter, intervention was not part of the job description. One such institution was the Supreme Court of the United States.