The United States Constitution does mention God. In Article VII, the Constitution states:
Done in Convention by the Unanimous Consent of the States present the Seventeenth Day of September in the Year of our Lord one thousand seven hundred and Eighty seven and of the Independence of the United States of America the twelfth....
I am often asked about this reference when answering questions about my book Was America Founded as a Christian Nation: A Historical Introduction.
The phrase "Year of our Lord," which is the only reference to God in the United States Constitution, was, of course, a standard eighteenth-century way of referencing the date. It reminds us that the Constitution was written in a different world than our own. Today we do not usually refer to the date this way. In the eighteenth century they did. The past is indeed a foreign country.
How did this reference to "the Year of our Lord" find its way into the Constitution?
We know that the phrase "Year of our Lord" was not included in the draft of the Constitution that was approved by the Convention. On Monday, September 17, 1787, James Madison moved that
the Constitution be signed by the members and offered the following as a convenient form viz. "Done in Convention, by the unanimous consent of the States present the 17th of Sepr. & c.---In Witness whereof we have hereunto subscribed our names."
After some more discussion that day (unrelated to the "Year of our Lord" phrase) most of the members voted to approve the document. The wording of the final clause that they approved was different from the wording that would eventually appear in the final Constitution. The new wording included the phrase "Year of our Lord."
In case you want to research this for yourself, check out:
Max Farrand, ed., The Records of the Federal Convention of 1787 Volume II, (New Haven: Yale University Press, 1911). pp. 643ff.
So, once again, how did this phrase make it into the draft we have today? I don't know. The phrase was not in the draft that the members of the Convention voted on and it may not have appeared on the draft that the framers signed. Daniel Dreisbach, in a 1996 article in the Baylor Law Review (Vol. 48, p. 967) suggests that the reference to "The Year of our Lord" at the end of the Constitution "may have been merely a scrivener's touch." (He also cites a 1991 doctoral dissertation from the University of Dallas: Archie P. Jones, "Christianity and the Constitution: The Intended Meaning of the Religion Clauses of the First Amendment, p.258, note 5).
The evidence available suggests that the phrase "Year of our Lord" was not part of the document approved by the members of the Constitutional Convention, but was probably added to the document sometime after the meeting.