Dendermonde was incorporated in the German Empire in 880 as a part of the Rijksvlaanderen (Imperial Flanders). After the withdrawal of the Northmen in 883, Count Boudewijn II of Flanders incorporated most of Imperial Flanders to his county. In the middle of the Xth century, there was a stone castle on the site of the current justice court, surrounded by the Dender and the Fish Canal. Merchants and travelers looking for a safe place built a town, whose wealth originated from the famous Dendermonde cloth. In the XIth century, the Count of Flanders transferred his rights on Dendermonde to the St. Bavo abbey in Ghent, that appointed the first lords of Dendermonde. The town defenses were increased with earth walls and canals. The Romanesque church was built to house the relics of the patron saints of the town, Sts. Hliduardus and Christiana. The town increased in the XII-XIIIth centuries and was surrounded with a town wall and gates. A Cistercian nun's abbey was founded near the Brussels gate in 1223; this was the first of a long series of monasteries, asylums, chapels, hospitals and leper-houses built in the town.
In 1233, Robrecht van Béthune granted a chart to the town, which wa then protected by four gates, a wooden "water fence" and iron chains on the Dender. The administrative and economic center of the town developed on the left bank of the Dender, with the building of wealthy houses by the merchants' guilds; a belfry, symbol of the municipal liberties, was built in 1337-1350. In 1347, the last lord of Dencermonde sold the town to the King of France, who transferred it the next year to the Count of Flanders Lodewijk van Male. In 1380, the militia from Ghent seized and plundered Dendermonde for the second time; the ruined town was incorporated in 1384 to the Duchy of Burgundy. Duke Philip the Handsome allowed a yearly market in 1397 and the town hall was rebuilt near the belfry.
