Before Connecticut had a colonial charter of its own, it had a document historians have long treated as an early landmark of self government. The Fundamental Orders of Connecticut, adopted in 1639 by the Congregationalist settlements Thomas Hooker had led out of Massachusetts Bay at Hartford, organized a civil government without requiring church membership as a qualification for voting, a real departure from Massachusetts Bay, where the franchise was tied to full membership in a gathered congregation. Hooker had preached that a wider circle of settlers deserved a political voice than Massachusetts Bay's leadership was prepared to grant, and taking his congregation overland to the Connecticut River valley let him build a colony on that conviction rather than continue arguing it from within Boston's establishment. Connecticut's Congregationalist churches nonetheless remained legally established, tax supported institutions for nearly two more centuries, not disestablished until 1818.
Yale, founded at New Haven in 1701 explicitly to train Congregationalist ministers, grew up inside that same established church system before becoming the secular university it is today, and Roman Catholicism, carried in by nineteenth and twentieth century Irish, Italian and Polish immigration, has since become the state's largest single tradition, thirty five percent of adults per Pew's 2023-24 study, in the same cities Congregationalism once governed alone.