Located in a position suited for defence, Bassano evolved in the Middle Ages thanks to companies Formed during the eleventh century for cutting of trees. The first building was just a small church dedicated to Our Lady of Tabernacles.
Thus the Fiefdom of Bassano was formed in the Papal States and Enotrio Serco was the first feudal lord in 1160.
In 1354 the estate was run jointly between the families Di Puccio, Savelli and Anguillara, and despite the Viterbo area being an area of clashes and power struggles, Bassano Romano had a quiet life. In 1428 the Anguillara came into possession also of a part of the fiefdom of Di Puccio and in 1482 Pope Sisto VI also assigned part of Savelli.
In 1566 the Anguillara ceded the fiefdom to the Giustiniani with Pope Clement VIII. These were a Genovese family that held a Aegean island, on the invasion of the Turks they returned to Italy in search of a quiet fiefdom. Their period featured works and improvements to the town and the completion of a palace, and in 1605 the lord of the Bassani fiefdom became a Marquis following a bull by Pope Paul V.
In 1644 Bassano Romano became a Principality and started receiving visits of popes and monarchs, including the English James III Stuart.
In the eighteenth century Bassano was affected by forms of contagious flu that decimated the population and brought misery. The coup de grace was given by the French troops of Napoleon plundering and pillaging the town twice in retaliation to its attempt to resist the French advance. And it was at this time that the devotion for the Our Lady of Mercy began.
In 1854 The principality passed to the Odescalchi who abandoned it.