Congregational leaders met again in Boston, Massachusetts in 1865, where they began to hammer out standards of church procedures (polity) and adopted a statement of faith, known as the Burial Hill Declaration.

Both denominations shared a Reformed theology; however, Congregationalists practiced a more decentralized form of church governance described in the Cambridge Platform.

[6] By the 19th century, Congregationalists were forming voluntary organizations for mutual cooperation and support among churches called associations.

By that time, Congregationalists had developed a greater denominational consciousness, which ultimately led to the 1865 Boston meeting where they began the process of establishing standards of church procedures (polity) and adopted a statement of faith, known as the Burial Hill Declaration.

[8] In 1927, motivated by the ecumenical movement, Congregationalists united with the Evangelical Protestant Church of North America.

This was a pietistic denomination of Swiss and German origin with about six thousand members, most of whom were located in the vicinities of Pittsburgh, Pennsylvania and Cincinnati, Ohio.

The church's mission was described as "to proclaim the gospel to all mankind, exalting the worship of the one true God, and laboring for the progress of knowledge, the promotion of justice, the reign of peace, and the realization of human brotherhood.

"[11] The Social Gospel flourished among Congregational churches, and the National Council pledged itself to work for a society that guaranteed a decent wage and denied privileges for the wealthy.

The five ideals include universal education, support for labor unions, the preservation and support of rural communities as well as price controls on agricultural products, the elimination of all forms of racial discrimination, and the abolition of all national armed forces except for internal police.

[11] The purpose of the National Council was to provide a forum to coordinate common programs and organizations of Congregational churches, such as managing a pension fund for Congregationalist ministers.

1917) was responsible for establishing and maintaining Sunday schools in addition to recruiting college students to staff them.