Witherspoon, the only clergyman to sign the Declaration, President of the College of NJ (Princeton) at the time, was a Scotch Presbyterian. There was brief celebration in the British camp during the time of the campaigns around Trenton and Princeton when there was word a tall clergyman had been shot and it was thought to be Witherspoon.
Also a signatory was Charles Carroll, of Carrollton, MD, one of the very few Catholics in the United States. He became the first Senator of the state of Maryland.
Rev. John Carroll, SJ, was the priest summoned by President George Washington to administer last rites. Washington had greatly admired the fervent support of Catholics on the battlefield, and strongly countered inclinations among certain Revolutionaries to discriminate against Catholics. In 1789, Rev. Carroll had been summoned to England to be ordained the first Catholic bishop, Archbishop of Baltimore. The selection of someone so intimately tied to the Revolution itself was widely seen as an enthusiastic endorsement of the American Revolution by the papacy. The Catholic priests had been careful to receive assurances from the Continental Congress of the Confederation that the elevation of a bishop, loyal to Rome, would not be seen as disloyal to the Republic. Rather, the appointment was most welcome, and seen as a natural demonstration of separation of Church and State.