Rufus King was also a U.S. Senator in the First U.S. Federal Congress (1789-1791).
Rufus King was an Episcopalian and (according to some sources) a Congregationalist.
He was identified as an Episcopalian by A Worthy Company: Brief Lives of the Framers of the United States Constitution by M. E. Bradford. the Library of Congress was cited as the source stating he was later a Congregationalist. (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), page 182:
...at the age of 72, in 1827, he died... He was laid to rest near King Manor in the cemetery of Grace Episcopal Church, Jamaica, Long Island, N.Y.
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.