Capestrano is a town located atop a hill (465 meters) in the central part of the Tirino Valley, which in Roman times was called Valle Tritana or Valle Trita. The Tirino River flows through the valley, known since Roman times as Tirinum flumen, as it originates from three sources (Capodacqua, Lago, and Presciano], all situated within the territory of Capestrano.
This is why the town's coat of arms features a castle from whose foundations three springs (trium amnium) emerge, which also gave rise to the name Capestrano, derived from the contraction of "Caput trium Amnium," meaning the Beginning of three springs. In the valley, during Roman times, there existed the thriving and populous city of Aufinium, a cultural center and home to a renowned philosophical school, so much so that the Romans elevated it to the rank of "municipium." The inhabitants belonged to the historic and well-known Vestini group and remained loyal to Rome for a long time. Pliny the Elder left a mention of ancient Aufinium, reporting the settlement in the Tirino Valley among the main Vestini centers: "Vestinorum Angulani, Pennenses, Peltuinates quibus iunguntur Aufinates Cismontani."
During the second half of the 6th century, the valley was occupied by the Lombards, who caused significant damage to Aufinium, disrupting the very structure of its territory and depriving it of any possibility of recovery. Houses were abandoned, and the population was forced to seek refuge elsewhere. The Lombard rule lasted for at least two centuries, during which the Lombard element mixed with the local population. The current origins of the village are traced back to around the year 880 when it seems to have formed by the clustering of small population nuclei that had scattered in the valley after the destruction of the city of Aufinium. Initially, it was under the dominion and authority of the Benedictine monks of the great Abbey of San Pietro ad Oratorium, located not far from the town.
The first document mentioning the name Capestrano dates back to 1284 when Charles I of Anjou, as a recognition for the loyalty shown in the conquest of the Kingdom of Naples, transferred control of the Tirino Valley territory to Riccardo Acquaviva di S. Valentino. The town was originally fortified, as evidenced by certain documents in which it was called "Oppida Capistrani." The need for defense is confirmed by the construction of a small watchtower at the Forca di Penne pass, where bands of Saracens had appeared.
Capestrano, from the second half of the 15th century, was a marquisate with the annexation of the barony of Carapelle, thus including all the towns in the Tritan Valley. In 1584, it became a principality that included Forca di Penne, the hamlet of Santa Pelagia, the fortress of Castel del Monte, and the barony of Carapelle.
Throughout its history, it was a fief of various noble families such as the Acquaviva, Accrocciamuro, Piccolomini, Medici of Tuscany, and finally, the Bourbons of the Kingdom of Naples and the Two Sicilies. Ferdinand IV of Bourbon granted Capestrano the title of a city. In 1860, it became part of the Kingdom of Italy.