First Unitarian has been part of the consolidated Unitarian Universalist Association of Congregations in North America since 1961. The Unitarian name comes from the church's affirmation of the oneness of God and rejection of the trinitarian belief that God, Jesus and the Holy Spirit are united in a divine nature. Universalism is the concept that God will redeem all, including those who do not believe in Christ.
Originally incorporated as All Souls Unitarian Parish in 1893 and renamed in 1913, it is the oldest Unitarian church in Oklahoma, Texas, Louisiana and Arkansas. The congregation met in at least seven locations before ground was broken in 1928 for the present building.
The church now has about 350 members, ages 14 and older.
Attendance averages about 150.