Richard M. Johnson was a Baptist.
From: Peter Roberts, "Richard Mentor Johnson" page in "God and Country" section of "Science Resources on the Net" website (http://www.geocities.com/peterroberts.geo/Relig-Politics/RMJohnson.html; viewed 23 November 2005):
Religious Affiliation: Baptist
Views on Religion and Politics:
Johnson was a strong supporter of the separation of church and state. During the late 1820s, there was a large movement, particularly among the clergy, to reverse the then current practice of providing mail service on Sunday, which they asserted was a violation of the Sabbath. Johnson, who was at that time the chairman of the Senate committee which oversaw the Post Office, looked into the matter. He issued a Report on the Subject of Mails on the Sabbath, in which he declares that, since the government is "a civil, and not a religious institution," it should not be bound by religious strictures. Sunday mail service continued. (See: Ken Lynn, "The Sunday Mail Debate," Freethought Today, October 1997)
"What other nations call religious toleration, we call religious rights. They are not exercised in virtue of governmental indulgence, but as rights, of which government cannot deprive any portion of citizens, however small. Despotic power may invade those rights, but justice still confirms them. Let the national legislature once perform an act which involves the decision of a religious controversy, and it will have passed its legitimate bounds. The precedent will then be established, and the foundation laid for that usurpation of the Divine prerogative in this country, which has been the desolating scourge to the fairest portions of the old world. Our Constitution recognises no other power than that of persuasion, for enforcing religious observances. Let the professors of Christianity recommend their religion by deeds of benevolence -- by Christian meekness -- by lives of temperance and holiness. Let them combine their efforts to instruct the ignorant -- to relieve the widow and the orphan -- to promulgate to the world the gospel of their Savior, recommending its precepts by their habitual example: government will find its legitimate object in protecting them. It cannot oppose them, and they will not need its aid. Their moral influence will then do infinitely more to advance the true interests of religion, than any measures which they may call on Congress to enact." -- Report on the Transportation of Mail on Sundays, 1829