Patrimonium Sancti Petri

The expression Patrimonium Sancti Petri, or shorter Patrimonium Petri, meaning 'Patrimony of (Saint) Peter', originally designated the landed possessions and revenues of various kinds that belonged to the Church of St. Peter (i.e. the Pope) at Rome.

Until the middle of the 8th century this consisted wholly of private property, but the term was later applied to the States of the Church, and more particularly to the Duchy of Rome.

The Roman Emperor Constantine the Great in AD 321 declared the Christian Church qualified to hold and transmit property. This was the first legal basis for the possessions of the Church of Rome. Subsequently they were augmented by donations. Constantine himself probably gave the Church the Lateran Palace in Rome. Constantine's gifts formed the historical nucleus for the network of myth that gave rise to the forged document known as the "Donation of Constantine".

Wealthy families of the Roman nobility followed Constantine's example. Their memory frequently survived, after the families themselves became extinct, in the names of the properties they once presented to the Roman See. During his reign, Pope Sylvester became the owner of properties in Italy, Sicily, Antiochia, Asia Minor, in the area of Hippo in North Africa, Armenia, and Mesopotamia. The donation of large estates ceased about 600 AD. The Byzantine emperors preferred the patriarchate of Constantinople, and were less liberal in their gifts. The wars with the Lombards likewise had an unfavourable effect, and few families were still in a position to bequeath large estates.

Apart from a number of scattered possessions in Dalmatia, and southern Gaul, the patrimonies were naturally for the most part situated in Italy and on the adjacent islands. Lands in Dalmatia and Illyricum were lost during the Avar and Slavic invasions. The most valuable and extensive possessions were those in Sicily, about Syracuse and Palermo. The revenues from these properties in Sicily and Lower Italy were estimated at three and one-half talents of gold in the eighth century, when Byzantine Emperor Leo the Isaurian confiscated them.

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Wikipedia