Pompeii, along with much of the surrounding regions of Campania, was finally integrated into Roman rule as an allied city in the early 3rd century BC after the Samnite Wars. The city became an important transit point for goods arriving by sea and heading to Rome or the rest of southern Italy along the nearby Appian Way.

Abundant information on Pompeii's public life dates back to the 2nd century BC. As the availability of written documents increases, it is revealed that the city was under the administration of an annually elected magistrate and a council composed of former magistrates. However, this form of government changed due to the city's involvement in the Allied War, between 91 and 89 BC, in which the Italic socii (allies) fought against the Romans for not granting them Roman citizenship. During the conflict, Sulla besieged and took the city in the spring of 89 B.C. After the Social War, the inhabitants of Pompeii, like other Italics, finally obtained full Roman citizenship through the lex Plautia Papiria, which definitively incorporated them into Roman Italy with the status of municipium.

A significant political event for Pompeii occurred in 80 B.C., when Sulla modified the city's status, transforming it from municipium to colonia in order to settle his veterans of the Greek wars. The city was officially called Colonia Cornelia Veneria Pompeiana, with "Cornelia" referring to Sulla's nomen and "Veneria" to Venus, the divinity that protected him. After the administrative reorganization of Italy carried out by Augustus, Pompeii was included in Region I Latium et Campania until its destruction.