State law could forcefully advance Christian moral ideas because the First Amendment’s ban on the establishment of religion, like the entire Bill of Rights, did not apply to the states. When the Bill of Rights was drafted in 1789, six states paid churches out of the public treasury. Under the First Amendment, states could do as they wished with respect to religion, whether that meant paying churches with public money, establishing an official religion, or doing nothing at all. Although the practice of paying churches came to an end in the fifty years after the Bill of Rights was instituted, the elimination of this funding mechanism did not change the special place that Christianity had within American law. For example, in many states office holders were required to take Christian oaths, and censorship laws were used to prosecute anything officials considered offensive to Christianity.
Slowly, though, Christian authority became unstable. By the end of the nineteenth century, judges began to reject the explicitly religious rationale for moral laws, though they often found ways to uphold them on some ostensibly secular basis. But judges eventually grew skeptical of even that. By the 1920s, jurists were becoming open to the emerging social sciences, which sought a nonreligious basis for understanding human society. The courts drew upon this new disciplinary knowledge to formulate a pluralistic vision of American society that denied the special place of Christianity within American law. The goal, as Supreme Court Justice Owen Roberts explained, was to create a body of law in which “many types of life, character, opinion and belief can develop unmolested and unobstructed.”
The key to this pluralistic vision was the Fourteenth Amendment, which gave the federal government power to protect Americans from the state-level infringement of constitutionally protected rights. Although the amendment was passed after the Civil War, it was not until the 1920s that the Supreme Court began to use it to create a more pluralistic legal framework. At first, liberals on the Court sought to protect political dissenters by applying federal free speech protections to the states. But the protections offered by the Court soon expanded. In the 1940 case Cantwell v. Connecticut, the Court applied the free exercise clause of the First Amendment to the states. Seven years later, in School District of Abington Township v. Schempp, it also applied the establishment clause to the states.