The state chartered Ansonia as a borough of Derby in 1864, and later as a separate town in 1889. In 1893, Ansonia incorporated as a city, consolidating with the boundaries of the town.
The state of Connecticut chartered Ansonia as a borough within Derby in 1864 and later granted it independent status as a town in 1889. In 1893, Ansonia officially became a city by incorporating its territory with the existing town's boundaries.