The Massachusetts Conference, United Church of Christ, began as a series of independent regional ministers’ associations. Originally these groups met to discuss matters of theology; as they formalized they took on the practice of ordaining clergy (in earlier Congregational polity the province of local churches). The earliest records of this collection date to 1722 from the Plymouth Association of Ministers. One important predecessor of the Massachusetts Conference was the Massachusetts Missionary Society, established in 1799 to send clergy to remote areas of Maine and New York and to establish new churches. The General Association of Massachusetts was established in 1808 to sanction the sending of the first missionaries of the American Board of Commissioners for Foreign Missions. The General Association and Missionary Society merged in 1927.

In the twentieth century the Congregational churches, and the Massachusetts Conference, were shaped by denominational mergers, beginning with a union with the Christian Connection in 1931. The Congregational Christian churches spent several decades achieving a merger with the Evangelical and Reformed Church, which was completed in 1957. In the midst of these conversations, the Conservative Congregational Christian Conference (CCCC) separated in 1948; and those who did not wish to merge with the UCC established the National Association of Congregational Christian Churches (NACCC).

For further information about individual Association and Conference, look at collection level for historical notes.