First Congregational Church of the United Church of Christ, Boulder, is the oldest existing congregational church in the state of Colorado. It was organized July 17, 1864, in a cottonwood grove near Valmont Butte, with 14 original members. Later Boulder was chosen as the site for the church over Valmont, as Boulder gave promise of being the future business and educational center and the county seat. From 1865 to 1875 the Reverend Nathan Thompson was pastor of the church, the first full-time minister in Boulder.
The Congregationalists met in a frame schoolhouse, at 15th and Walnut, until they built their first church in 1866–1870 on what is now the site of the Carnegie Library. The church, known then as The Congregational Church of Boulder Valley (the church became officially First Congregational Church of Boulder in 1887), chose to build on the hillside site so its tower would be visible for miles down the valley, attracting people to worship.
The original bell, which had been brought overland by ox-team in 1869, was the first church bell in Boulder County. It now stands on a stone base in front of the present church.
As the church grew, the congregation felt the need for a larger building. The real impetus for a building fund came from an anonymous gift of $10,000, which was offered by an Easterner if matching funds could be raised. By February 1906 ground was broken for the present church building.
Although the basement of the new building, now Plymouth Hall, was used as early as 1907, the building was not completed until 1908. For two years while the church was under construction, worship was held in the Physician's Building at 14th and Spruce.
The church was dedicated on January 12, 1908. It is the oldest standing Congregational Church in Colorado. A number of well-known Boulder citizens of the time played important roles in its construction: Marinus G. Smith hauled sand from his farm whenever it was needed, Andrew J. Macky provided supporting posts and timbers, Tourtelott and Squires and their twin wives were financial donors.
The Gothic Revival style building was designed by Thomas MacLaren, an internationally known Colorado Springs architect, who also designed Boulder's Carnegie Library.
Noteworthy architectural features include the asymmetrical façade of Boulder sandstone in hammer-squared ashlar pattern, pointed arch tracery windows with stained glass, the crenelated tower with its stone gargoyles, narrow slit openings and tall narrow windows with wooden louvers, and its unique side entrance ramp. The ramp's original intent was for ease of rolling coffins in and out of the church. Today it is used as the main entrance and offers handicap access to the sanctuary. The ornamental hinges on the original main entrance doors, as well as those on the Broadway entrance, are exact copies of those at Durham, the oldest cathedral in England.
There are only a few visible changes on the outside of the original structure: the removal of the iron lamp posts at the bottom of the front stairs, the addition of outside doors and stairs from the basement of the southwest corner of the building to ease access to the Christian Education Building, and the installation of the bell from the original church on a stone base in front. The newest addition is the International Peace Pole, inscribed in six languages, erected on the Broadway side of the church in January, 1992.
First Congregational Church was designated an historical landmark in 1975.