When the Court took up the First Amendment in the twentieth century, the meaning of free speech had changed little in 100 years. No speech cases came before the Court during the nineteenth century, and, consequently, the legal understandings of freedom of speech at 1800 and 1900 were essentially the same: the amendment imposed a restriction only on Congress and its essential purpose was to deny Congress the power to impose prior restraints. It did not impose restrictions on the states, nor did it protect individuals from being punished for the content of their speech. The primary legal tool for evaluating the appropriateness of speech was the bad tendency test, the British common law principle that allowed judges and juries to consider what might have happened as a consequence of a statement. What actually did happen was beside the point. If the Court could imagine a plausible set of negative events resulting from an individual's statement, he could be convicted of sedition on the basis of this fabricated scenario.
Two things, however, would force the Court to revisit these old understandings of the First Amendment. The first was the development of the doctrine of incorporation. This legal doctrine states that, under the due process clause of the Fourteenth Amendment, the federal government must protect Americans' liberties from violations by the state governments—and free speech is one of the liberties requiring protection. Subsequently, the Court would have to assess the constitutionality of several state laws dealing with speech.
In addition, World War I would lead Congress to pass two laws aimed at curbing speech deemed dangerous to the war effort. These Espionage and Sedition Acts would force the Court to consider the compatibility of federal restrictions on speech with the protections offered by the First Amendment.