The Society was established in 1833 and has been worshiping in its historic Gothic Revival Sanctuary since 1844.
The Sanctuary is adorned with stained glass windows and a Louis C. Tiffany angel mosaic.
After meeting in rented halls and buying a building on Adams Street, the members purchased the current site and secured Minard Lafever as architect.
Over the years, three other Unitarian societies were formed, flourished and eventually rejoined the First Church.
Prominent in the history of the First Unitarian Church is a tradition of social ministry that includes youth work, a settlement house for immigrants, support for the Civil Rights Movement and opposition to the Indo-China war.