According to Justice Hugo Black’s majority opinion in Everson v. Board of Education, “The First Amendment has erected a wall between church and state. That wall must be kept high and impregnable.” The landmark 1943 Supreme Court case challenged the legality of a New Jersey law allowing reimbursement for transportation to Catholic schools. The case is important less for its decision regarding the law—it upheld it—than for the reasoning behind it.

First, it was the earliest case to assert that religious freedom is protected not only from laws made by the Federal Government, but also from laws made by the states. Second, Justice Black’s opinion included the first comprehensive judicial interpretation of the Establishment Clause of the First Amendment.