The pope, the bishop of Rome, claims spiritual authority over more than a billion Catholics worldwide. He also exercises temporal authority over a tiny enclave of Rome consisting of the Vatican Palace, Saint Peter's Basilica, and 44 hectares with the ancient Leonine Walls. As sovereign of the Vatican City States, he has around 1,000 subjects, mostly clerics.
While those facts are widely known, many are not familiar with the fact that before the reunification of Italy in the late 19th century, the popes were rulers not only of the city of Rome but of much of central Italy for over a thousand years. The Papal States, as they are usually referred to, were formally gifted to the Church by the Frankish King Pepin III (AD 751 - 768) in 756, but the origins of the Papal States can be traced back over 150 years earlier.
One of the most prominent figures in the foundation of the Papal States was Pope Gregory I, who led the Roman Church and the city of Rome from AD 590 - 604. During his time, Rome enjoyed the prominence in Italy it once had before being sacked in the late fifth century, and Pope Gregory I helped ensure that the Eternal City would shape the destiny of Western Europe, not the Byzantine capital of Constantinople.
In the wake of the Western Roman Empire's collapse, kings across Western Europe continued to maintain the appearance of imperial unity and claimed the status of lawful subjects of the Eastern Roman Empire, then based out of Constantinople.
