More concretely, the Equal Protection Clause, along with the rest of the Fourteenth Amendment, marked a great shift in American constitutionalism. Before the enactment of the Fourteenth Amendment, the Constitution protected individual rights only from invasion by the federal government. After the Fourteenth Amendment was enacted, the Constitution also protected rights from abridgement by state governments — henceforth they could not, among other things, deprive people of the equal protection of the laws. What exactly such a requirement means, of course, has been the subject of great debate; and the story of the Equal Protection Clause is the gradual explication of its meaning.
For a long while after the Clause became a part of the Constitution, it was interpreted narrowly. During and after World War II, however, the United States Supreme Court began to construe the Clause more expansively. During the 1960s, the other two branches of the federal government — the executive and the legislative — joined in, as Congress and the President passed and enforced legislation intended to ensure equality in education, employment, housing, lodging, and government benefits. While an expansive reading of the Clause was undercut, to some extent, by Court decisions of the 1970s and 1980s, the Equal Protection Clause remains an integral part of U.S. constitutional law.