The Roman Republic was the period of ancient Roman civilization when the government operated as a republic. It began with the overthrow of the Roman monarchy, traditionally dated around 509 BC, and its replacement by a government headed by two consuls, elected annually by the citizens and advised by a senate. The Roman Republic saw an extended period of political instability, including several civil wars, from circa 133 BC to 30 BC, which ultimately saw the end of the Republic and the arrival of the Roman Empire in its place. As the Roman Republic was never formally abolished, the exact date of its transition into the Empire is a matter of debate, but the most commonly accepted date is 27 BC, when Octavian Caesar adopted the title of "Augustus."
The government of the United States of Atlantis was closely based on the Roman Republic, with a Senate headed by two Consuls who could hold each other in check with veto power. The Atlantean Army was made subject to the Senate, with the Consuls personally overseeing it in wartime, to further ensure that the nation would not fall under military rule.
When the Federated Commonwealths of America declared independence from England in 1738, they used the Roman Republic as a template for the new nation, in its style of government with a two-headed executive branch, Latin slogans on important monuments and offices, the naming of currency units, and, less admirably but luckily only for less than a century, the institution of slavery.