William Leigh Pierce was an Episcopalian.
From: Political Graveyard website (http://politicalgraveyard.com/bio/pierce.html#RB60V6FQY; viewed 7 December 2005):
Pierce, William Leigh (1740-1789) - of Savannah, Chatham County, Ga. Born in 1740. Major in Continental Army during the Revolutionary War; member of Georgia state house of representatives, 1786; Delegate to Continental Congress from Georgia, 1787; member, U.S. Constitutional Convention, 1787. Episcopalian. Member, Society of the Cincinnati. Died in Savannah, Chatham County, Ga., December 10, 1789. Burial location unknown.
Note that numerous sources and authoritative references have been consulted in order to ascertain the religious affiliation of the American Founding Fathers. Note that the excerpts and references mentioned on this page are not the only references used in order to identify this person's religious affiliation.