In 1462, thanks to the will of Pope Pius II, the powerful Assisian family of Fiumi can boast the title of "Counts of Sterpeto". In this way the dismemberment of the county and of the castle itself from the Commune of Assisi to the family so devoted and faithful to the Church is confirmed.
The new era of Sterpeto and its castle coincided with the rebirth of the fierce disputes between the Oddi and the Baglioni. The Fiumi family sided with the first and suffered heavy assaults by enemy soldiers until the loss of the castle itself. Only the intervention of Pope Innocent VIII and his legate, Cardinal Francesco Silvio Piccolomini, managed to bring the county under control of the Fiumi taking advantage of the war that broke out between the cities of Foligno and Spello.
Giacomo and Alessandro Fiumi, in 1511, stipulated an agreement concerning the communion of goods that provided for the death of the first of the two brothers, the current lord of Sterpeto, the designation of the second as administrator of the estate. In 1535, after Sforza Fiumi, Count Cesare, who married Almena Baglioni and participated in the wars of Carlo V against the Lutheran, became lord of Sterpeto. Taking on the role of lieutenant of the Pontifical Arms.
The confirmation of the river flooding, brought by Pope Paul III, was a meaningful event for this county. "For greater caution - we read in the discourse of the bridge in 1546 - again we grant and assign in fief, with the usual census of a pound of silver, the Castle of Sterpeto, with its territory, with woods and woods, waters and fish ponds, rights, jurisdictions and appurtenances ... to you and to your male descendants in a straight line ... and you and your posterity forever invest in them and infect us ... ".
From some files kept in the Historical Archives of Assisi it is clear how the Fiumi had organized a real small state in these lands, with lots of podestà (nominated every six months), bailiff, tax officials, court, notary, soldiers and a real prison with tetrified and local cramps, strains for torture and traps. The jurisdiction of the accounts, with the passage of time, widened a lot to influence in the seventeenth century men and things of Rocchicciola, S. Gregorio, Coltraticce, Collepune, Monte Villano, Mora, Torre Chiagina, Petrignano and others.
The confines of the properties of the Conti Rivers were a matter of continuous and confused discussion among the latter, the Municipality of Assisi and also the Papal Curia. Throughout the century, documentations speak of city councils, intense exchanges of letters, delegations of men arrived in the county and disputes in progress. Certainly it is that Sterpeto and its castle continued to be considered an autonomous reality until the nineteenth century.
In 1684 the male direct line broke off. Guido Fiumi, married to Eleonora, was in fact the last of the dynasty because he had no sons. The feud consequently fell back to the Chamber. Countess Almena, her sister, stayed with Paolo Emilio Roncalli, her son. The latter assumed the surname Fiumi and got back the County of Sterpeto.