Verona is a city rich in history … and drama. It predates Rome, and was an ally of the Roman Empire for many years before it became an important Roman municipum in 49 BC. Its history endures from ancient times through the turbulent Middle Ages, when the city gained great power and influence; during the Renaissance, when our story is set, Verona had gone through many changes in leadership, from the Germans to the Venetians to the Spanish, to the French, and back again to the Venetians.
It's important to remember that Italy as a country did not exist until much later; each city/state in Italy functioned independently, with alliances, politics and wars both within and between their walls.
Shakespeare's Verona is an artificial one; it mirrors some aspects of the real world, but simplifies the politics for the sake of his story. The real ruler of Verona at the time of the play was the Republic of Venice and its doge.
What does ring true in his tragedy of Romeo and Juliet is the constant, sometimes violent struggles for power between merchant families … the Montagues and the Capulets are inventions, but plenty of examples exist of very real houses in similar bloody feuds. Assassinations were common, as were street brawls, and the threat of violence was just as ever-present as the amazing art and architecture of the time.
History of Verona (UNESCO)
Verona and Romeo and Juliet (VeronaFor2)