The fortified village, of Byzantine origin, was in fact repopulated in the early Middle Ages by some Slavic populations coming from the territory of Schiavona, today Dalmatia with the name of Castro degli Schiavoni. In its history it had several feudal lords, last of which were the marquises De Sangro and its population at the end of '400 welcomed for a short time the Albanian refugees who then settled in the nearby Casalvecchio. In 1863 it was renamed Castelnuovo della Daunia.
The village differs from all the other villages of the Monti Dauni thanks to an airy and orderly urban structure, marked by wide streets and large squares, which are framed by palaces and beautiful churches. Among its main monuments are the thirteenth-century Church of the Madonna della Murgia and the sixteenth-century Church of Santa Maria Maddalena with the adjoining convent, the Roman Palace, the Church of San Nicola, the Church of the Incoronata.
Castelnuovo has a pleasant territory, mainly hilly, characterized by beautiful views and the presence of springs of mineral waters, thanks to which has arisen a modern Spa, the only one in the Province of Foggia.