Answer
After the death of Numa Pompilius, the Romans elected Ancus Marcius to be their second king. He was the son of Numa Pompilius's daughter and a Marsi chieftain. Ancus Marcius ruled for 24 years, during which time he built a harbor at Ostia and a bridge across the Tiber. He also extended the boundaries of Rome to the sea. Ancus Marcius assigned his nephew Lucius as guardian of his sons.