Protestant denomination in the United States, formed by the union of the Evangelical and Reformed Church and the General Council of Congregational Christian Churches. Each was the result of former unions. Negotiations toward union of the two bodies were begun in 1942, and during the next 15 years there were seven revisions of the Basis of Union. The United Church of Christ was formed in a General Synod on June 25, 1957, and its constitution was declared in force on July 4, 1961.