Thomas Jefferson's famous reference to a "wall of separation between church and state" comes from a letter he wrote on January 1, 1802, to the Danbury Baptist Association in Connecticut.
Here is the essential context:
* The Quote: In the letter, Jefferson wrote: "Believing with you that religion is a matter which lies solely between Man & his God, that he owes account to none other for his faith or his worship, that the legitimate powers of government reach actions only, & not opinions, I contemplate with sovereign reverence that act of the whole American people which declared that their legislature should 'make no law respecting an establishment of religion, or prohibiting the free exercise thereof,' thus building a wall of separation between Church & State."
* The Purpose: The Danbury Baptists were a religious minority in Connecticut, where the Congregational Church was still the state-established religion. They had written to Jefferson expressing concern about religious freedom. Jefferson used the letter to reassure them that the federal government would not interfere with religious matters or establish a national church.
* Legal Status: It is crucial to note that Jefferson was not the author of the First Amendment (he was in France during its drafting) and this letter was not a law. It was a private correspondence explaining his interpretation of the First Amendment's Establishment Clause ("Congress shall make no law respecting an establishment of religion...").
* Historical Impact: While largely ignored for decades, the phrase "wall of separation" was revitalized in the 20th century. In the 1947 Supreme Court case Everson v. Board of Education, Justice Hugo Black cited Jefferson's letter to establish the principle that the First Amendment requires a strict separation of church and state, a precedent that has shaped American constitutional law ever since.