OAK PARK, Ill.— On Sept. 26, several hundred people in festive dress gathered in Unity Temple, Frank Lloyd Wright’s iconic building in Oak Park, Ill., for a reception and chamber music concert. The anniversary event, held 100 years to the day after the temple’s inauguration, was both celebration and fundraising benefit, a somewhat bittersweet occasion organized by the Unity Temple Restoration Foundation.

The gala began with guests gathering in the loggia at sundown for a cocktail buffet, and later moved into the main sanctuary for a chamber music concert that included a Beethoven quartet and a world premiere — “The Coming of Light,” a new composition by noted American composer Peter Lieberson, commissioned especially to mark the occasion, thanks to support from gala benefactor Sidney Robinson. The Chicago Chamber Musicians and guest baritone John Michael Moore performed, to an enthusiastic reception by the audience — which included Mr. Lieberson.

There were also brief remarks from Board President Rebecca Cooke, who quoted from the temple’s 1909 dedication ceremony, reiterating the hope that it would continue to “exert a refining and elevating influence on all who enter its portal.” Certainly, the evening was elevating to the attendees, who returned to the loggia for a celebratory toast and a commemorative birthday cake in the shape of the building, before leaving with the spoils of a silent auction (mostly lower-priced, donated items).

Since its completion, Unity Temple has been recognized internationally, not only by Frank Lloyd Wright admirers, but to the architecture and design community and a broad segment of the general public. An early design by the iconoclastic architect, who built his own home as well as a number of his Prairie-style houses in Oak Park and its environs, it was one of the earliest buildings in an identifiably modern style. It was also one of the first to be made entirely of reinforced cast concrete. Wright chose the material both for its flexibility and its modest cost — he was working on a budget of just $45,000 — and the casting was done entirely on site.

A member of Oak Park’s Unitarian congregation, Wright was commissioned to design a new church when the previous one burned down. The church was to be located on a long but fairly narrow rectangular corner lot on a busy street in the relatively new suburban community just west of Chicago.

Wright’s design reflected his own aesthetic, but also met the needs of the congregation, which sought both a place of worship and a community meeting space that suited the distinctly liberal and inclusive Unitarian approach to religion. The building he designed, in two cruciform-shape sections separated by a passageway, has little in common with the usual church structure. It has no imposing street entrance — visitors enter via half-concealed stairs on either side of the building — and where one would expect to find a steeple there’s only the flat, overhanging roof characteristic of Wright’s Prairie Style buildings.

The façade is somewhat forbidding, with massive ornamental concrete pillars decorated with abstract geometric designs, and is windowless — maintaining privacy and minimizing street noise. The interior, however, is another story; entering through glass doors on either side of the loggia area, guests are welcomed by a warm color scheme of autumnal hues and an inviting ambience that carries throughout the flowing spaces. Ingeniously placed stained-glass strip windows surround the building just below roof-level, filtering light in from all sides, and stained-glass inserts punctuate the coffered ceiling of the sanctuary to make it function as a skylight. Warm wood strips carry the eye around the interior, emphasizing the horizontality of the space, which is adorned at each corner by Wright-designed hanging light fixtures. The pews are not set in the usual facing-front style, but in a U-shape configuration, allowing parishioners, on the main level and two balconies, to look at one another as well as toward the pulpit, which is no more than 45 feet away from any seat. The result is a welcoming air of community befitting the democratic Unitarian approach.