The formal establishment of a Unitarian Society in Utah dates from February 1891, and the history of the Unitarian movement relates to the growth of religious liberalism in Utah. In a general sense, Unitarianism is part of a tradition of truth-seeking based on human reason which is manifest in positions are in agreement with trinitarian Christian doctrines concerning God and Jesus of Nazareth. Trinitarian interpretations were formally embraced at the Council of Nicea in the year 325. Followers of dissenting beliefs were branded heretics; doctrine was no longer related to reason but to tradition only. All freedom of thought, discussion, belief, or teaching of differing viewpoints was a crime, often punished with death. Thus, differing thought and inquiry pushed underground to surface through the following centuries in various forms, only to be attacked with all possible dispatch.

The Unitarian denomination has venerable European and British Island roots commencing at the time of the Protestant Reformation. Its development in the United States preceded the American Revolution in a number of the old congregational churches of New England.

Unitarians are opposed to a central authority and devoted to three leading principles: complete free religious thought rather than bondage to creed or dogma; unrestricted use of reason in religion, rather than reliance upon external authority or past tradition; and generous tolerance of differing religious opinions and usages, rather than insistence upon uniformity in doctrine, worship, or polity.

Formal organization in the United States (although many churches did not join the association for fear it would impede their freedom) commenced in 1820, and in 1825 became the American Unitarian Association (AUA). Unitarians have always been involved in essentially religious but scrupulously non-sectarian, humanitarian social action. Unitarians were involved in the struggle against slavery and were important to the success of the Abolitionist movement. Unitarians and Universalists have pioneered in human welfare causes and movements; they include Susan B. Anthony in woman's suffrage, Dorothea Dix in prison reform and the treatment of the mentally ill, and Horace Mann in the cause of public education. Unitarianism has never attracted a large number of adherents, but its liberal influence in general religious thought has been significant. Also it has greatly promoted and enhanced education and the establishment of libraries and schools.

The organization of the First Unitarian Society of Salt Lake City took place on the evening of Wednesday, 24 February 1891, in the parlors of the Walker House. The society chose its first board of trustees (nine members), which elected Nat M. Brigham as president, and forty-six people signed their names to a three-page constitution. Sunday services commenced the following Sunday in the Salt Lake Theater with Rev. David Utter speaking to audiences of from 300 to 400 people. The Sunday School was started the summer of 1891, and had a recorded enrollment of 113 six month later. In September this same year the Ladies Unitarian Society organized as a separate body "for the purpose of promoting the welfare of the Church, good fellowship, charitable and intellectual endeavors." Emily M. Almy was elected president. On 17 April 1893 the society was formally incorporated under the laws of the Territory of Utah.

History of Unitarianism in Utah was written and published in 1896. It is believed Margaret Benson Hudson was the author, but no know copy is know to exist. From September 1899 through March 1901 there were no business meetings, no elections of officers, and no social activities. On 20 April 1901 the AUA reorganized the society, and by 1903 efforts to construct a building began. A lot was purchased at 138 South 200 East and on 5 November 1903 the first meeting was held. This location served the membership until September 1926 when the building was sold to Trinity Baptist Church. A new site for the church was selected and purchased at 569 South 1300 East in May 1926. During the construction period, the Unitarians met at the Ladies Literary Club on South Temple. The new church was dedicated on 4 September 1927.

During the general assembly in May 1961 the American Unitarian Association merged with the Universalist Church of America (which traditionally proclaimed a universal salvation for all after death as opposed to a "hellfire and damnation" for the wicked) to form the Unitarian Universalist Association. The Salt Lake Unitarians also decided on a change of name; at the annual meeting on 26 January 1962 a constitutional amendment was proposed, discussed, and carried, changing the name to the First Unitarian Church of Salt Lake City.

Twenty-five ministers served the society/church in the one hundred years it has been a part of the Territory and State of Utah. Its contribution is significant. The records of First Unitarian Church of Salt Lake City, which comprise seventy-six linear feet of shelf space, are housed in the Manuscripts Division, Special Collections, Marriott Library, at the University of Utah. The first known Unitarian sermon delivered in Salt Lake City - given by Reverend Sam Eliot on the 30 November 1890 at the Salt Lake Theatre - is one of the documents stored there. Eliot was minister of the Denver Unitarian Church and director of the Rocky Mountain Unitarian Conference; he visited Salt Lake City for the express purpose of forming a broad, non-sectarian "People's Church." The collection of historical materials (including photographs) has been processed and a register prepared. Additional sources of information are the interviews of former ministers, presidents of the board of trustees, and other prominent Unitarians whose reminiscences are transcribed and available in the Everett L. Cooley Oral History Project, Marriott Library, University of Utah.

In May 1981, after talk of establishing a second Unitarian Society in the Salt Lake Valley had been prevalent for twenty years, a meeting was held to form a steering committee. On 22 April 1983, the second society, named the South Valley Unitarian Universalist Society, with twenty-five members, was chartered by the Unitarian Universalist Association. Robert Goff was elected president of the board of trustees. The Reverend Donn Marcussen was called as full-time minister in 1985. The membership in May 1991 was 115 adults, with 60 children enrolled in the religious education growth and learning program.

November 1990 saw commencement of a fund-raising drive for $300,000, to enlarge the Salt Lake City facilities for religious education and social activities. The goal was passed in May 1991 with pledges at over $400,000. The Centennial celebration of the organization of the Unitarians in Salt Lake City took place on Sunday, 24 February 1991.

The South Valley Unitarian Universalist Society's co-ministers have recently been involved in organizing two new congregations: an Ogden group and a Park City group. In addition, there are expressions of interest in Unitarianism in other areas of the state, including Utah County. The Unitarian Church remains a vital part of the state entering the twenty-first century. Unitarians are the forefront of social issues, including promoting women's, minority, and gay rights, as well as caring for the homeless, promoting peace, and protecting the environment.