Maasdam was founded nearby a substantial castle on the banks of the river Maas, the remaining foundations of which were discovered in 1958 in a parcel of land near the road in Maasdam known as "Kromme Elleboog". For a long time, it was assumed that the ruins in Maasdam were those of the castle Duivestein. However, it has more recently been suggested that the ruins could instead be those of a castle that belonged to the Lords of Weede. The area with castle ruins in Maasdam is officially protected as a Rijksmonument. Most of the village of Maasdam and surrounding areas, including the castle, were destroyed during the second St. Elizabeth's flood (1421), although the main dyke in Maasdam as well as the hamlet and polder of Sint Anthoniepolder and hamlet of Cillaarshoek survived. Successful restoration was hindered by further floods as well as the Hook and Cod Wars but eventually Maasdam was restored to its former size soon after Philip the Good allowed his treasurer Jan Nemery, who had been the vassal of Maasdam for almost two decades, in 1435 to reclaim the polders next to the surviving dyke in Maasdam from the sea. Former vassals of Maasdam   The last vasal of Maasdam, Frans Adam van der Duyn van Maasdam (1771 -1848), was one of the three noblemen who briefly formed the provisional government of the Netherlands after its liberation from Napoleonic France by Prussian and Russian troops in 1813. He was part of the Triumvirate that declared the Sovereign Principality of the United Netherlands in 1813 and invited William Frederick, Prince of Orange-Nassau to return from exile in England and accept sovereignty over the principality. Kees Verkerk, Olympic speed skater