One reason the debates over the French Revolution became so heated was that Americans were unsure about their own religious future. The Illuminati scare of 1798 was just one manifestation of this fear. Across the United States, a slow but profound shift in attitudes toward religion and government was underway.

In 1776, none of the American state governments observed the separation of church and state. On the contrary, all thirteen states either had established (that is, official and tax-supported) state churches or required their officeholders to profess a certain faith. Most officials believed this was necessary to protect morality and social order. Over the next six decades, however, that changed. In 1833, the final state, Massachusetts, stopped supporting an official religious denomination. Historians call that gradual process “disestablishment.”

In many states, the process of disestablishment had started before the creation of the Constitution.  South Carolina, for example, had been nominally Anglican before the Revolution, but it had dropped denominational restrictions in its 1778 constitution. Instead, it now allowed any church consisting of at least fifteen adult males to become “incorporated,” or recognized for tax purposes as a state-supported church. Churches needed only to agree to a set of basic Christian theological tenets, which were vague enough that most denominations could support them.

Thus, South Carolina tried to balance religious freedom with the religious practice that was supposed to be necessary for social order. Officeholders were still expected to be Christians; their oaths were witnessed by God, they were compelled by their religious beliefs to tell the truth, and they were called to live according to the Bible. This list of minimal requirements came to define acceptable Christianity in many states. As new Christian denominations proliferated between 1780 and 1840, however, more and more Christians would fall outside of this definition. The new denominations would challenge the assumption that all Americans were Christians.

South Carolina continued its general establishment law until 1790, when a constitutional revision removed the establishment clause and religious restrictions on officeholders. Many other states, though, continued to support an established church well into the nineteenth century. The federal Constitution did not prevent this. The religious freedom clause in the Bill of Rights, during these decades, limited the federal government but not state governments. It was not until 1833 that a state supreme court decision ended Massachusetts’s support for the Congregational church.

Many political leaders, including Thomas Jefferson and James Madison, favored disestablishment because they saw the relationship between church and state as a tool of oppression. Jefferson proposed a Statute for Religious Freedom in the Virginia state assembly in 1779, but his bill failed in the overwhelmingly Anglican legislature. Madison proposed it again in 1785, and it defeated a rival bill that would have given equal revenue to all Protestant churches.  Instead Virginia would not use public money to support religion. “The Religion then of every man,” Jefferson wrote, “must be left to the conviction and conscience of every man; and it is the right of every man to exercise it as these may dictate.”

At the federal level, the delegates to the Constitutional Convention of 1787 easily agreed that the national government should not have an official religion. This principle was upheld in 1791 when the First Amendment, with its guarantee of religious liberty, was ratified. The limits of federal disestablishment, however, required discussion. The federal government, for example, supported Native American missionaries and Congressional chaplains. Well into the nineteenth century, debate raged over whether postal service should operate on Sundays, and whether non-Christians could act as witnesses in federal courts. Americans continued to struggle to understand what it meant for Congress not to “establish” a religion?