A tribe occupied one of the hills dominating the valley, called the Ouche du Fort. The city developed around the castle and its church built on a rocky outcrop, an abrupt overlooking the Lay.
The trade is developed by the road and the barges that go up the little river from the ocean.
After the revolution in 1822, the parishes of Mareuil, Beaulieu-sur-Mareuil and St André-sur-Mareuil merge.
In the Napoleonic era, a national road was drawn, leading to the construction of a new stone bridge. In 1974 Mareuil sur Lay teamed up with Dissais, to form the town of Mareuil on Lay-Dissais.
The commune extends on 25.7 km² and approaches 3000 inhabitants.
The Church of Saint-Sauveur is an exceptional building of the heritage of the town, classified historical monuments and then July 14, 1877.Edifié the XIIth century on the site of a former priory, the Church of Saint-Sauveur is characterized by his Romanesque style.
In 1568, during the Wars of Religion, the church was looted and set on fire. After some very basic restorations, it is burned again during the Revolution. Abandoned for several decades, restoration work began in 1877, under the leadership of Father Guérineau.
The west facade, the bell tower and the restoration of the choir date from this time. Between 1964 and 1967, the work was completed, restoring its original appearance to this nine-century-old monument.
The Church Saint-Sauveur, noble and beautiful by its surfaces, its volumes and its proportions, is a masterpiece of the Vendée Romanesque art.