William Ellery was a Congregationalist and a devout Christian.
He was identified as a Congregationalist by The Congregationalist Library. (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 49:
As a patriot and a Christian, his name will ever be revered.
William Ellery, the colleague of Stphen Hopkins, of Rhode Island, in the Continental Congress of 1776, was born at Newport, on the twenty-second of December, 1727. His father paid particular attention to his early education, and when qualified, he placed him in Harvard College, where he was distinguished as a close student, particularly of the Greek and Latin languages. He graduated in 1747, at the age of twenty years, with the most honorable commendations of the faculty. He chose the profession of the law as a business, and when he had completed his studies, he commenced practice in Newport, then one of the most flourishing places in the British American Colonies.From: Robert G. Ferris (editor), Signers of the Declaration: Historic Places Commemorating the Signing of the Declaration of Independence, published by the United States Department of the Interior, National Park Service: Washington, D.C. (revised edition 1975), pages 51-52:
For twenty years, Mr. Ellery practised law successfully, and acquired a fortune. When the troubles of the Revolution began, and, as an active patriot, he ejoyed the entire confidence of his fellow-citizens -- he was called into public service. Rhode Island, although not so much oppressed as Massachusetts and New York at the beginning, was all alive with sympathy; and the burning of the Gaspee, inProvidence Bay, in 1772, and the formal withdrawal of the allegiance of the Province from the British crown, by an act of her legislature, as early as May, 1776, are an evidence of the deep, patriotic feeling with which her people were imbuded. She promptly responded to the call for a general Congress, and Stephen Hopkins and William Ellery were sent as delegates.
Mr. Ellery was a very active member of Congress, and on the second day of August, 1776, he signed the Declaration of Independence.
In 1778, Mr. Ellery left Congress for a few weeks, and repaired to Rhode Island, to assist in a plan to drive the British from the island. It proved abortive, and many of the inhabitants were reduced to great distress. Mr. Ellery exerted his influence in Congress, successfully, for their relief. About the same time he was one of a committee to arrange some difficulties in whch Silas Deane, and other commissioners sent to Europe, were involved. He was also a member of another committee to arrange some difficult matters connected with the admirality courts. In each capacity, his wisdom and sound discretion made him successful.
In 1782, Mr. Ellery was designated by Congress to communicate to Major Genreal Greene, their estimates of his valuable services in the Southern Campaigns. In 1785, he was one of a committee to whom the definitive Treaty of Peace with Great Britain was referred. At this time, he was a judge of the Supreme Court of Rhode Island. In connection with Rufus King, of New York, he made strong efforts in 1785, to have slavery in the United States abolished. After the new constitution was adopted in 1788, and the new government was put in operation, he was appointed collector for the port of Newport, which office he retained until his death, which occurred on the fifteenth of February, 1820, in the seventy-third year of his age. As a patriot and a Christian, his name will ever be revered.
One of a small group of lesser known signers whose achievements were comparatively modest, William Ellery gained little fame beyond his hometown... among his grandchildren were William Ellery Channing, influential theologian and apostle of Unitarianism, and Richard Henry Dana, Sr., noted poet and essayist.