John Langdon was also a U.S. Senator in the First U.S. Federal Congress (1789-1791).
John Langdon was a Congregationalist.
He was identified as an Congregationalist by: the Library of Congress and A Worthy Company: Brief Lives of the Framers of the United States Constitution, written by M. E. Bradford. (Source: Ian Dorion, "Table of the Religious Affiliations of American Founders", 1997).
From: Robert G. Ferris (editor), Signers of the Constitution: Historic Places Commemorating the Signing of the Constitution, published by the United States Department of the Interior, National Park Service: Washington, D.C. (revised edition 1976), pages 182-184:
Langdon... also enjoyed long and fruitful careers in New Hampshire and national politics... He sat again in the legislature (1801-5), twice holding the position of speaker. After several unsuccessful attempts, in 1805 he was elected Governor and continued in that post until 1811 except for a year's hiatus in 1809... In 1812 Langdon refused the Democratic-Republican Vice-Presidential nomination on the grounds of age and health... he died at the age of 78. His grave is at Old North Cemetery in Portsmouth.
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.