The ancient Caiatia was already in the hands of the Romans in 306 BC, and since in the 3rd century BC it issued copper coins with a Latin legend it must have had the civitas sine suffragio. In the Social War it rebelled from Rome, and its territory was added to that of Capua by Sulla. In the imperial period, however, it was once more a municipium.[3]
Caiazzo was the seat of anti-royal rebellions at the times of the Neapolitan Republic, and also housed several Carbonari. Despite this, Caiazzo was one of the few towns in the kingdom whose population sided against Garibaldi's expedition which annexed southern Italy to Piedmont.
Caiazzo has remains of Cyclopean or polygonal masonry walls, and under the Piazza del Mercato is a large Roman cistern, which for centuries continued to provide a good water supply.[3]
