Congregationalist
Split from: Anglican but embraced Calvinism - first organized in 1616 in London, England - the official church of most of New England till well after the American Revolution. They sent out missionaries to start General Associations in NY, Great Lakes States, Illinois, Kansas etc.
Records: The early town records of the New England states are civil records but were designed by the Congregationalists so that they not only record town business but the births, marriages and deaths of residents. Because Congregationalism was essentially the state religion if your family chose something else prior or in the decades immediately following the American Revolution they will often make a statement in the records that they are Baptists etc. or that they do not follow the majority religion.
Congregational Christian Historical Society - the protestant puritan movement that settled New England became known as Congregationalists. If you had a New England minister in your family or a later Congregationalist minister check here at their large database of obits for clergy and missionaries
CT: Fairfield Co.: Records of the Stamford Congregational Church