Thesis advisor: James M. O'Toole / This dissertation examines the religious environment in nineteenth-century Massachusetts created by church disestablishment and a theological schism. Congregationalists, bound to God and to one another with a sacred covenant, were the traditional beneficiaries of the state's constitutional requirement that towns raise tax revenue for "the support and maintenance of public Protestant teachers of piety, religion, and morality." The nation's last church establishment system was not removed until a statewide referendum in 1833, but, in practice, it had eroded earlier as Congregational churches encountered internal and external religious dissent. The mechanics of the establishment system had often been used by residents, including those liberal church members who eventually adopted the name Unitarians, to obstruct orthodox Congregationalists from operating more than 100 local churches in Massachusetts. These changes compelled Congregationalists to voluntarily support their churches prior to formal disestablishment, effectively ending the establishment system town-by-town and removing those churches from the center of town life. The lived religious experiences dramatically changed. Laymen took advantage of Congregationalism's inherently decentralized structure and gained control of their local churches. They sought to maintain the purity of their individual covenants by expelling absent members and those espousing theological heresies. In the process, local ministers were marginalized and dismissed with increasing frequency. Tensions arose between many in the clergy elite, who advocated for denominational consistency, and the laymen, who defended the autonomy of their local church. The story of antebellum Congregationalism in Massachusetts, rather than being part of an emerging national denominationalism, was actually one of an inward turn, a type of atomization of the religious denomination. The uncoordinated actions on the local level helped prompt the first national gathering of Congregationalists in more than two centuries, but suggestions for the adoption of explicitly "Congregational" elements by local churches were rejected by the laity. Congregationalism emerged from the Civil War with these antebellum changes made permanent and entrenched as a parochial, laity-driven denomination. / Thesis (PhD) — Boston College, 2014. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: History.