In the plain at the confluence of the two rivers Liri and Rio Spallo Basso was the ancient Roman colony of ‘Interamna Lirenas’ (between two rivers), founded in the fourth century BC to control the Samnites. The Romans moved 4,000 settlers with their families here and perhaps in this area there were already areas inhabited by the Volsci.
The colony was destroyed during the Barbarian invasions and around a thousand people took refuge on a hill in a small castle, called Terame or Termini.
The small town was subjected to the Benedictine Abbey of Montecassino and here in 1018 they created a garrison to defend themselves from the lords of Aquino. As a result of the wars between the Papacy and the Empire, during the reign of Frederick II, the inhabitants abandoned the castle.
The area has been re-populated but during the wars of partition between Spain and France, fought along the Garigliano, Pignataro had an inexorable decline of population.
In 1487 it became part of the Kingdom of Naples. In the eighteenth century, the population grew but the town remained small: a road and a row of one-story houses.
During World War II the town was razed to the ground because it was located along the Gustav Line, the German defensive front.