The town's name is linked to the cult of San Marzano, Bishop of Tortona, while the second part of its name, probably derives from the ancient olive cultivation, widespread in the area, but there is no harmony about these definitions among the local historians. It is a municipality in the province of Asti, located in a high position: it stands out as a small group of houses between the green of the nearby environment, dominated by the steeple of the local parish church. From its privileged position, the town features a spectacular panorama on the Monte Viso and the surrounding hills. The tranquility and beauty of the landscape have always been a strong draw for tourists from around the World. It was chosen as residence by the famous German artist Mollerstaedt, whose works are often on exhibition in the town. San Marzano is also famous for the production of apples and important wines, including Barbera.
It is believed that the first inhabitants of the area were the Ligurian, expelled by the Romans that conquered and colonized the area. It is widely believed that the ancient castle was built in the place of settlement of the Roman era. During the medieval period the town and other nearby municipalities were involved in the contrasts between the Marquis of Monferrato and the Lords of Asti and Alessandria. During the XIV century it was under the rule of local Lords of the Asinari Family. Their dominion resisted throughout the following centuries and in 1808 Filippo Antonio Maria Asinari was proclaimed Senator and Regent of the Region.

Not to miss:

- the Parish Church of San Marzano, located in the courtyard of the castle. it was built in the XIII century, enlarged in the second half of the XVIII and finally restored in 1843. Built in Renaissance style, it features a single nave plan and preserves inside paintings dating from the XIX century attributed to the artist Ivaldi;
- the Church the Battuti, a church formerly entitled to Saints Peter and Paul, it was built under the stables of the castle in the early XVIII century and later enlarged by the addition of the sacristy;
- the four rural Churches of St. Anthony, the Santissima Annunziata, San Rocco and Santa Libera;
- the Castle, perhaps of Roman origins, it was built before the year 1000 and was enlarged and fortified in 1217 by the Lords of the Asinari Family, that had the four towers built, one at each corner. In the second half of the XVII the heirs of the same Asinari Family transformed it into the private residence.