After Romulus' strange and mysterious death, the kingship fell to Numa Pompilius. Though first unwilling to serve as king, his father convinced him to take up the position as a service to the gods. Celebrated for his natural wisdom, Numa’s reign was marked by peace and prosperity.

Numa reformed the Roman calendar by adjusting it for the solar and lunar year as well as by adding the months of January and February to bring the total number of months to twelve. Numa instituted several of Rome's religious rituals including the Salii, and a flamen maioris to serve as the chief priest to Quirinus, the Flamen Quirinalis. Numa organized the area in and around Rome into districts for easier management. He is also credited with the organization of Rome’s first occupational guilds.

Numa is remembered as the most religious of the kings (surpassing even Romulus), and during his reign, he introduced the flamens, the vestal virgins of Rome, the pontiffs and the College of Pontiffs. Under his administration, temples to Vesta and Janus were constructed. Also during his reign, it was said that a shield from Jupiter fell from the sky with the fate of Rome written on it. Numa ordered eleven copies of the shield to be created and these shields became sacred to the Romans.