The area had been inhabited since the Neolithic period, as shown by the finds along the river Fiora. The Etruscan presence is documented in the necropolis of Castro.
In the Middle Ages it was the church’s property, and in the thirteenth century Ischia passed to Orvieto, that granted it to the Farnese.
In the Middle Ages the village had formed around a castle that the Farnese subsequently turned into a palace. In 1537, the Farnese decided to make a Duchy of this territory and to elect the village of Castro as its capital. The story begins when Pope Paul III entrusted the Duchy of Castro to his son Pier Luigi.
The city was entirely designed by Sangallo the Younger and when he died the town was almost finished. But the plot thickens as Pier Luigi Farnese had moved to Piacenza, where he died two years later, and the duchy passed to his nephew Ottavio. The Farnese had always been at odds with the Church and Castro held out until 1649, when it killed a bishop sent by Pope Innocent X who then ordered its destruction.
Today little remains of Castro while Ischia di Castro has grown and continued its story.
Under Pope Innocent X, then, Ischia returned to the Church and followed that fate until the unification of Italy.
In 1816 Pope Pius VII appointed the sculptor Antonio Canova ‘Marquis of Ischia‘, as a reward for the recovery of numerous works of art stolen by the army of Napoleon.