Because of its geographic prominence and the notable ministers who have served the congregation, the church is considered to be among the most historically important in Unitarian Universalism.

[2] Two future presidents of the American Unitarian Association—Samuel Eliot and Dana Greeley—served the church during its first hundred years in the Arlington Street building.

When the area around Federal Street became commercial, the congregation voted to move to newly filled land in the Back Bay neighborhood.

Designed by Arthur Gilman and Gridley James Fox Bryant, architects for the Old Boston City Hall, its exterior was inspired by St. Martin-in-the-Fields, London.

[6][2] The building is supported by 999 wooden pilings driven into the mud of Back Bay, and brownstone ashlar for its exterior was quarried in New Jersey.

[citation needed] The sanctuary, with its Corinthian columns and graceful rounded arches, was modeled after the Basilica della Santissima Annunziata del Vastato in Genoa, Italy.

[2] The panels on either side of the choir loft, containing the Ten Commandments and the Lord’s Prayer, were brought from the Federal Street Church, as was Dr. William Ellery Channing’s pulpit, which stands in the Hunnewell Chapel.

[2] The box pews, made of chestnut with black walnut rails, were at one time deeded to members of the congregation.

[5] The Arlington Street Church holds the complete set of Wilson's original watercolor design drawings for all the windows.

[11] After vandalism destroyed a memorial dedication pane in the 1970s, plexiglas sheets were installed on the exterior side of the Tiffany windows for protection.

Over time, the plastic discolored to a bluish tinge and transmitted less light, as an accumulated film of dirt also clouded the stained glass.

[12] After a 50-year period when the Tiffany windows were only viewed by the congregation, the church is now open to the general public from 10 a.m. to 3 p.m. daily from mid-May through the end of October, except Sunday and when special events are scheduled.