It is more likely the settlement arose during the early Middle Ages, perhaps starting around a small defensive element, a watch-tower guarding a route important for that time.

The documents from the XI century confirm the existence of a well-defined settlement, a true castle, with fortifications and walls, inside which there are houses, a square, and places of worship.

From this moment on, Stroncone residents favor the Guelph faction; the coat of arms of the commune has the pontifical keys atop a white cross on red background.

According to Lanzi, in 1394 the fort was occupied by Pandolfo Malatesta and in 1404 by Andrea Tomacelli: on this latter occasion the fortress would have been partly destroyed by Stronconesi himself to get rid of the stately garrison and subsequently rebuilt, and by 1493, at the passage of Pius II Piccolomini, the place was noted to be "very full".

For this reason, as in other centers of the papal state (see the case of Rieti and Terni), beside the aisle palace, the headquarters of the local government, was built the apostolic palace, the peripheral seat of the central government, with the residence of the governor and the annexed jails, an expression of the judicial power that the governor exemplified.

Among the most significant modern events, was the resistance sustained by the inhabitants of Stroncone against the French troops of Napoleon, which penetrated the town walls only after a siege of seven days and deceit.