Initiaully upon its founding in 1842, the First Unitarian Society of Milwaukee had a small presence in the city. It initially appealed to settlers from New England around the Yankee Hill neighborhood. By the time the congregation built the present church in 1892, the church had grown even more liberal in its beliefs. This departure from traditional Christianity attracted a growing number of interfaith members. Unitarianism in Milwaukee has expanded significantly since the 1960s, both in terms of membership of the First Unitarian Society and the establishment of three Unitarian congregations in surrounding communities. You can see the church's full history here.