On this day in 1789, President George Washington violated the yet-undreamed of "separation of church and state" by leading the nation in a day of national prayer and thanksgiving for the new Constitution.
The modern myth of "separation of church and state" really means a separation of God and government. Not a single person alive in 1789 imagined that the new federal Constitution created a "secular" government, that is, a government that believed it could ignore God with impunity, rather than a government "Under God."
Read about George Washington's promotion of the True Religion here:
Government-Sponsored Prayer and Thanksgiving to the True God