Founded as the First Church of Killingly, Killingly's oldest congregational church is now known as Westfield Congregational Church, United Churches of Christ. According to a historical sketch in a 1905 booklet, the church was begun in 1715. That same pamphlet goes on to trace the church's history, minister to minister, through almost two centuries. After the date of the pamphlet, the church did join the United Churches of Christ. The church does not appear to have its own website, although its contact information can be located using Google.
The current home of the church's records is unclear. According to an article on American Ancestors, they are not part of the Connecticut State Library's slip index but likely are still held by the state. A phone call to the church may clarify the situation. Recent records are likely held by the church.
Cemetery records are available on Find A Grave. The cemetery is called the Westfield Cemetery.