Throughout its history, UUCA has taken part in progressive causes from the Civil Rights Movement to the legalization of same-sex marriage in Virginia.

Meeting spaces included the Buckingham Community Room, Ashton Heights Women's Club, and Kate Waller Barrett School.

The church purchased a 1.07 acre (0.43 ha) lot at the intersection of present-day Arlington Boulevard and South George Mason Drive.

[5] In November 1948, ground was broken on the church's first building, located at 4451 1st Place South, with assistance from the American Unitarian Association which gave the congregation a $15,000 loan.

The organization was founded to assist with establishing additional Unitarian congregations in the Washington, D.C., metropolitan area, and All Souls and the Arlington church were its first members.

[4] The congregation began planning for a new facility and chose Charles M. Goodman, a prominent local architect known for his modernist work, to design the church building.

A church committee wrote that it was "confident that Mr. Goodman’s concept of design, his wide experience, and his original and creative genius promise for us a distinctive building which will portray in structural form the spirit and aspiration of this congregation."

Church leaders invited the congregation to give suggestions for Goodman's design which included "an architectural style which would express the inspiring tradition of Unitarianism in Virginia" and a "free form and no stained glass, [resulting in] a building to represent our cleavage with the past.

"[5] The congregation wanted the building to "reflect their liberal, progressive beliefs and that would signify the UUCA's leadership position within the denomination.

His design included plans for a main sanctuary and adjoining wing, the latter which was not built at the time due to budget concerns.

[5] The total cost was approximately $300,000, and the dedication was held on March 22, 1964, with a sermon by Dana McLean Greeley entitled "Building a Faith for the Future.

The new wing, designed by Kerns Group Architects of Washington, D.C., and built by Dustin Construction, Inc. of Gaithersburg, Maryland, was dedicated on October 2, 1994.

[3][1][8] One of the church's leaders said "We're hoping by it being put on the national registry, people will realize that the physical presence of a group in a community matters.

[11][12][13] Like other Unitarian congregations, UUCA is a liberal church that has been active in social justice causes and interfaith dialogue throughout its history.

In 1949, a time when most local organizations were segregated, the church operated a children's summer camp open to all races.

During the 1950s, the church was one of the few places in Northern Virginia where black and white individuals met to discuss race relations and ways to improve society.

In 1951, UUCA minister Ross Allen Weston founded the Community Council for Social Progress, an interracial, interfaith group that promoted "full development of democratic principles in human relationship".

[14] In June 1956, UUCA minister Weston, who was also president of the Unitarian Fellowship for Social Justice, received a letter of gratitude from Martin Luther King Jr.[15] Following the landmark 1954 Supreme Court decision, Bolling v. Sharpe, which made segregation in Washington, D.C.'s public schools illegal, Virginia Governor Thomas B. Stanley sought input from the state's citizens.

[5] In October 1958, the church received a bomb threat the morning of a sermon by Rabbi Emmet A. Frank of Temple Beth-El.

This was part of a larger effort by the American Nazi Party, headquartered in Arlington, to intimidate synagogues and other institutions affiliated with or friendly towards Judaism.

The bomb threat was widely condemned by area churches and the Arlington congregation released a statement saying it would not be intimidated, harassed, or coerced to change the way it practiced religion.

[17][18] From the 1990s until it was demolished in 2011, Reeb Hall was rented out to nonprofit groups including the Northern Virginia chapter of Habitat for Humanity and Arlington Street People's Assistance Network.