The phrase "Founding Fathers" is a proper noun. It refers to a specific group of men, the 55 delegates to the Constitutional Convention. There were other important players not in attendance, like Jefferson, whose thinking deeply influenced the shaping of our nation. These 55 Founding Fathers, though, made up the core.
The denominational affiliations of these men were a matter of public record. Among the delegates were 28 Episcopalians, 8 Presbyterians, 7 Congregationalists, 2 Lutherans, 2 Dutch Reformed, 2 Methodists, 2 Roman Catholics, 1 unknown, and only 3 deists--Williamson, Wilson, and Franklin--this at a time when church membership entailed a sworn public confession of biblical faith.[1]
This is a revealing tally. It shows that the members of the Constitutional Convention, the most influential group of men shaping the political foundations of our nation, were almost all Christians, 51 of 55--a full 93%. Indeed, 70% were Calvinists (the Episcopalians, Presbyterians, and the Dutch Reformed), considered by some to be the most extreme and dogmatic form of Christianity.
Benjamin Franklin
Even Franklin the deist is equivocal. He was raised in a Puritan family and later adopted then abandoned deism. Though not an orthodox Christian, it was 81-year-old Franklin's emotional call to humble prayer on June 28, 1787, that was the turning point for a hopelessly stalled Convention. James Madison recorded the event in his collection of notes and debates from the Federal Convention. Franklin's appeal contained no less than four direct references to Scripture.
And have we forgotten that powerful Friend? Or do we imagine that we no longer need His assistance? I have lived, sir, a long time and the longer I live the more convincing proofs I see of this truth: that God governs in the affairs of men. And if a sparrow cannot fall to the ground without his notice, is it probable that an empire can rise without His aid? We have been assured, sir, in the sacred writings that 'except the Lord build the house, they labor in vain that build it.' I firmly believe this and I also believe that without His concurring aid, we shall succeed in this political building no better than the builders of Babel.[2]