The Roman Empire was formally declared in 27 B.C. when the Senate granted Gaius Octavius the title Augustus, creating the first emperor of the Roman civilization. The period of Imperial Rome followed the Triumvirate period of civil wars and a 500 year-old republic.
The 200 years that followed the establishment of the Roman Empire were an era of expansion, prosperity and political stability known as the "Pax Romana," or "Roman Peace." During this time, the Empire grew to encompass 70 million people, roughly 21 percent of the world's population at the time. It would survive for 500 years, suffering division and civil war through the majority of the period. The Roman Empire ultimately fell in the West in 476 A.D. with the deposition of the Emperor Romulus Augustulus.