How did it start?
Unitarian Universalism is a liberal religious tradition formed from the consolidation of two religions: Unitarianism and Universalism. Both began in Europe hundreds of years ago. The Universalist Church of America was founded in 1793, and the American Unitarian Association, 1825.
Originally, all Unitarians were Christians who didn't believe in the Holy Trinity of God (Father, Son, Holy Ghost), but in the unity, or single aspect, of God. Many of the founding fathers were Unitarians, and Thomas Jefferson, for example, held strong Unitarian beliefs. Unitarian beliefs stressed the importance of rational thinking, a direct relationship with God, and the humanity of Jesus. As for Universalism, it emerged as a Christian denomination with a central belief in universal salvation; that all people eventually will be reconciled with God.