The United Church of Christ did not begin as one thing splitting into pieces, the way many American denominations did. It began as two already blended traditions choosing, after decades of quiet conversation, to become one. The first was the Congregational Christian Churches, itself an 1931 union of the historic Congregationalists of New England, self-governing since the Pilgrims and Puritans of the seventeenth century, with the Christian Connection, a small non-creedal movement born on the American frontier. The second was the Evangelical and Reformed Church, formed in 1934 when the Reformed Church in the United States, tracing to German and Swiss settlers of colonial Pennsylvania, joined the Evangelical Synod of North America, a body of German Lutheran and Reformed background shaped by Prussia's own nineteenth century church union.
Bringing these two already merged bodies together meant joining two different systems of church government: the Congregational Christian Churches' fiercely local, congregation first polity, and the Evangelical and Reformed Church's more connectional, synodical structure inherited from continental Europe. Negotiators worked through a Basis of Union that let each local church keep title to its own property and the final say over its own affairs, a compromise letting congregational independence and connectional cooperation coexist rather than compete. Delegates ratified the union at the Uniting General Synod, held in Cleveland, Ohio, in 1957, and the United Church of Christ was born describing itself as united and uniting, a denomination assembled from parts that were themselves already assemblies.