Robert Morris was an Episcopalian.
He was identified as an Episcopalian 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: B. J. Lossing, Signers of the Declaration of Independence, George F. Cooledge & Brother: New York (1848) [reprinted in Lives of the Signers of the Declaration of Independence, WallBuilder Press: Aledo, Texas (1995)], page 98:
This misfortune, and the inroads which asthma had made upon his constitution, proved a canker at the root of his bodily vigor, and he sunk to rest in the grave, on the eighth day of May, 1806, in the seventy-third year of his age, leaving a widow with whom he had lived in uninterrupted domestic happiness for thirty-seven years... In 1769, Mr. Morris married miss Mary White, sister of the late venerable Bishop White, of Pennsylvania.
From: B. J. Lossing, Signers of the Declaration of Independence, George F. Cooledge & Brother: New York (1848) [reprinted in Lives of the Signers of the Declaration of Independence, WallBuilder Press: Aledo, Texas (1995)], page 96:
When Congress fled to Baltimore, on the approach of the British across New Jersey, Mr. Morris, after removing his family into the country, returned to, and remained in Philadelphia. Almost in despair, [George] Washington wrote to him, and informed him that to make any successful movement whatever, a considerable sum of money must be had. It was a requirement that seemed almost impossible to meet. Mr. Morris left his counting-room for his lodgings in utter despondency. On his way he met a wealthy Quaker, and made known his wants. "What security can'st thou give?" asked he. "My note and my honor," promptly replied Mr. Morris. The Quaker replied: "Robert, thou shalt have it." -- It wsa sent to Washington, the Delaware was crossed, and victory won!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 197-199:
Merchant Robert Morris was a man of many distinctions. One of the wealthiest individuals in the Colonies and an economic wizard, he won the accolade "Financier of the Revolution," yet died penniless and forgotten. He and ROger Sherman were the only signers of all three of the Nation's basic documents: the Declaration of Independence, Articles of Confederation, and Constitution. Morris... also served as a Senator in the First Congress...
Robert [who lived in Philadelphia at the end of his life] died in 1806 in his 73rd year and was buried in the yard of Christ Church.