Dayville Historic District is a historic district in the town of Killingly, Connecticut. The district was added to the National Register of Historic Places in 1988. The community or village of Dayville was named after Capt. John Day, who owned the water privileges on the Five Mile River. With the opening of the Norwich and Worcester Railroad in 1830, Dayville also became a hub for freight transport for other manufacturing villages along the river. By 1849, the village had grown sufficiently in population to have its own church, the Dayville Congregational Church, a Greek revival building built by Alexander Blanchard. The church was heavily damaged in a hurricane in 1938. Killingly Intermediate School is located in the area.