The name of the town derives from “sa ia majore”, the main Roman road, perhaps to be associated with the road that connected Tharros to the Forum Traiani baths (Fordongianus). Built in medieval times, Siamaggiore has a historic centre with rural architecture which is typical of the Campidano area: low houses with wide courtyards and narrow streets, mostly built with raw earth bricks called ladiri.
The parish church is dedicated to Saint Costantino, an example of late eighteenth-century Baroque architecture, while the church of San Ciriaco, just outside the town, is of Romanesque origin.
Siamaggiore is a town with a strong agricultural vocation, it is nestled in the flat and productive territory of the lower Tirso valley. The reclamation of a portion of the territory where the agricultural village of Pardu Nou was built, and where the sanctuary of Santa Maria stands, dates back to the twentieth century.
Among the products of excellence there is certainly the Artichoke, to which a traditional festival is dedicated and takes place at the start of spring.