James Garfield was a Disciple of Christ. He was a member of the Stone-Campbell (Restoration Movement) denomination known as the "Christian Church (Disciples of Christ)."
From: Peter Roberts, "James Abram Garfield" page in "God and Country" section of "Science Resources on the Net" website (http://www.geocities.com/peterroberts.geo/Relig-Politics/JAGarfield.html; viewed 29 November 2005):
Religious Affiliation: Disciples of Christ
Summary of Religious Views:
In his early adulthood, Garfield sometimes preached and held revival meetings.
"I not only never introduced such a resolution as that to which you refer -- but in several public speeches I have praised the wisdom of our fathers for prohibiting Congress from legislating on the subject of religion -- and leaving it to the voluntary action of the people." -- letter to Robert G. Ingersoll, 9 July 1880, denying claims that he had introduced legislation in support of government support for religious education.
"The Constitution guarantees absolute religious freedom. Congress is prohibited from making any law respecting an establishment of religion or prohibiting the free exercise thereof. The Territories of the United States are subject to the direct legislative authority of Congress, and hence the General Government is responsible for any violation of the Constitution in any of them. It is therefore a reproach to the Government that in the most populous of the Territories the constitutional guaranty is not enjoyed by the people and the authority of Congress is set at naught. The [Church of Jesus Christ of Latter-day Saints] not only offends the moral sense of manhood by sanctioning polygamy, but prevents the administration of justice through ordinary instrumentalities of law.
"In my judgment it is the duty of Congress, while respecting to the uttermost the conscientious convictions and religious scruples of every citizen, to prohibit within its jurisdiction all criminal practices, especially of that class which destroy the family relations and endanger social order. Nor can any ecclesiastical organization be safely permitted to usurp in the smallest degree the functions and powers of the National Government." -- Inaugural Address, 4 March 1881