As the Greeks were creating urban culture and spreading it around the Mediterranean, other peoples, including the Etruscans and the people who later became the Romans, built their own societies on the Italian peninsula. The Romans spread their way of life throughout Italy by means of conquest and incorporation. After wars in which they defeated the wealthy city of Carthage, they expanded their political dominance throughout the western Mediterranean basin. Then they conquered in the East until they came to view the entire Mediterranean as mare nostrum, “our sea.” Yet their successes brought war and civil unrest, and they also brought transformations of Roman society and culture as these became Hellenized.

The final days of the republic were filled with war and chaos, and the republican institutions did not survive. Rome became an empire ruled by one man. The laws and administrative practices of the republic shaped those of the empire, however, as well as those of later states in Europe and beyond. When the American constitution was drafted in 1783, its authors—well read in Roman history and law—favored a balance of powers like those they idealized in the Roman Republic, and they chose to call the smaller and more powerful deliberative assembly the Senate. They, too, were divided into those who favored rule by traditional elites and those who favored broader political power, much like the optimates and populares of the Roman Republic. That division is reflected in the fact that the U.S. Congress has two houses, the House of Representatives elected directly by voters, and the Senate, originally elected indirectly by state legislatures.