According to the legend, Rome was founded in 753 BC by the twin brothers Romulus and Remus. Romulus became the first King of Rome, naming the city after him. In 509 BC an aristocratic Republic (res publica) was established. Augustus became the first Emperor in 27 BC, marking the end of the Roman Republic. The Roman Empire continued to expand until the 2nd century, following decline and end in 476. Rome became the center of Christianity and the capital of the Papal States until 1870.