The Roman Kingdom was the earliest period of ancient Rome, traditionally dated from 753 BC to 509 BC. It was characterized by a monarchical system, where kings ruled over the city-state. The kingdom is said to have been founded by Romulus, who became its first king after the legendary founding of Rome. During this time, Rome expanded its territory and established its social and political structures. The kingdom consisted of seven kings, each contributing to the development of Roman culture and governance. Notable kings included Numa Pompilius, known for his religious reforms, and Tarquin the Proud, whose tyranny led to the kingdom's downfall. The end of the Roman Kingdom marked the transition to the Roman Republic.