After the fall of Napoléon I, the Congress of Vienna reconstituted the Kingdom of the Netherlands under the rule of William I, including what would later be Belgium. William renamed the Departments "Provinces" and changed their names: the Department of Ourthe became the Province of Liège and the Department of Lower Maas became the Province of Limburg. However, the former capital of the Duchy of Limburg (the town of Limbourg) was already in the Province of Liège. The Province of Limburg was mostly constituted by the County of Loon; its only parts formerly ruled by Limburg were Valkenburg and s' Hertogenrad.
Belgium seceded from the Netherlands in 1830. The sharing of Limburg between the two neighbours was difficult. The "24 Articles' treaty", signed in 1839 only, allocated to the Netherlands the part of the Province of Limburg located east of the Maas. This is the origin of the two Belgian and Dutch Limburgs. The Dutch Limburg is still related to the historical Duchy of Limburg but the Belgian Limburg does not include a single piece of land formerly belonging to the Duchy, being mostly made of the former County of Loon.
