There's seven of them.
Arkansas1, Maryland2, North Carolina3, Pennsylvania4, South Carolina5, Tennessee6 and Texas7. They all have different clauses in their respective constitutions which say that people who don't believe in God (or, alternatively, A Supreme Being) can't hold public offices.
That's how many who actually try to enforce those laws.
In 1993, Herb Silverman, professor of math at the College of Charleston, tried to apply as notary public. In the pre-printed application there was an oath he had to sign, which ended with "so help me God". He crossed out the "God". His application was thus turned down.
Herb contacted the ACLU. They filed a lawsuit against the state of South Carolina. It took 4 whole years, but in 1997 the state Supreme Court ruled that the law was unconstitutional as it violated both the first and the sixth amendment.
Article 19, Section 1: "No person who denies the being of a God shall hold any office in the civil departments of this State, nor be competent to testify as a witness in any court".
Declaration of Rights, Art. 36: "...nor shall any person, otherwise competent, be deemed incompetent as a witness, or juror, on account of his religious belief; provided, he believes in the existence of God..."
Declaration of Rights, Art. 37: "That no religious test ought ever to be required as a qualification for any office of profit or trust in this State, other than a declaration of belief in the existence of God; nor shall the Legislature prescribe any other oath of office than the oath prescribed by this Constitution. "
Article 6, Section 8: "The following persons shall be disqualified for office:
First, any person who shall deny the being of Almighty God. "
Article 1, Section 4: "No person who acknowledges the being of a God and a future state of rewards and punishments shall, on account of his religious sentiments, be disqualified to hold any office or place of trust or profit under this Commonwealth."
Article 6, Section 4: "No person who denies the existence of the Supreme Being shall hold any office under this Constitution."
Article 9, Section 2: "No person who denies the being of God, or a future state of rewards and punishments, shall hold any office in the civil department of this State. "
Article 1, Section 4: "No religious test shall ever be required as a qualification to any office, or public trust, in this State; nor shall any one be excluded from holding office on account of his religious sentiments, provided he acknowledge the existence of a Supreme Being."
Article 4, Section 2: "No person shall be eligible to the office of Governor who denies the existence of the Supreme Being...."
Article 6, Section 2: "No person who denies the existence of the Supreme Being shall hold any office under this Constitution."
Yes, I realize that none of these laws will ever be tried in court. Yes, I realize that this isn't some kind of "MORAL OUTRAGE!". Yes, I realise that these laws carry as much weight as the silly laws you'll find anywhere. This is merely amusing trivia, and shouldn't be taken too seriously.
Tlachtga doesn't get it. The law does indeed protect people from religious discrimination - but it only protects people who "acknowledge the being of a God and a future state of rewards and punishments", meaning that you're free to discriminate against atheists without repercussions.