The area of Blera was inhabited by the Etruscans and it is thought that its name derives from the Etruscan plaise-ra, “the city of plaise” where plaise was the name of a person or a noble Plaisena family with three tombs in the necropolis.
The Etruscans had settled between the VIII and V century BC on the spur of tufa rock at the confluence of two streams, the Biedano and Rio Canale, a typical choice for their settlements.
The city was also commercially active due to a road linking Cerveteri and Tarquinia with the hinterland.
During the Roman period, many writers such as Strabo, Olinio the Elder and Ptolemy mention the name of Blera. The name was then to be changed in the Middle Ages to Bled and Bieda and was only again returned to Blera in 1952.
The city flourished during the Roman period as it was crossed by the ancient Via Clodia that connected Rome with Cosa and from where remain tracks embedded in the tuff and the two bridges of the Diavolo and the Rocca.
After the fall of the empire, it was among the first dioceses and it had bishops from 457 to 1093, when it was united with the diocese of Tuscania. The first bishop of Blera, San Vivenzio, is one of three patrons of the town together over San Sensia, Martyr who lived between the fourth and fifth centuries AD, and Sant’Ermete.
Blera gave birth also to a Pope, Pope Sabiniano I who ruled between 604 and 606.
In 772 it was destroyed by King Desiderio in response for the request of Pope Hadrian I for the return of the territories occupied by the Lombards.
From the thirteenth to the fifteenth century it belonged to the family of the Di Vico Prefects and in 1247 was destroyed for the second time. This time because of Frederick II of Swabia in retaliation against the Di Vico family, within the struggles between the Papacy and the Empire, between Guelfi and Ghibellines.
With the extinction of the Di Vico family, Pope Boniface IX in 1400 gave Blera to Counts Francesco and Nicola Anguillara. In 1465 Pope Paul II brought it under the direct control of the Holy See until 1516 when it was once again assigned to Anguillara, to Don Lorenzo Anguillara of Ceri.
In 1572 this family died out and Blera was governed by the Apostolic Camera until the unification of Italy.