The significant legal document that established the separation of church and state in America is the First Amendment to the United States Constitution, ratified in 1791. It prohibits Congress from making any law that establishes a religion (the Establishment Clause) or impedes the free exercise of religion (the Free Exercise Clause). This amendment was influenced by Enlightenment ideals and advocates like Thomas Jefferson, who emphasized religious freedom as a fundamental human right. The separation of church and state has been crucial in safeguarding both religious liberty and governmental neutrality regarding religion throughout American history.