The numerous archeological artefacts go back to the 8th century B.C. and testify to the first villages in the territory of San Costanzo, the beginning of the iron age which is identified, in the hilly centre, with the Piceni civilisation. One of the oldest and most important Picentini necropolis was found in San Costanzo.
Today the town has a fountain in piazza Perticari, which is surrounded by the castle walls, the civic tower and the imposing bulk of the Teatro della Concordia, built on what must have been the fortified Malaestiano-roveresco tower.
The festa della Polenta (the Polenta festival), is one of the oldest in the Marhes.