The Lords of Westerlo were the feudal lords of the fiefdom (called 'Heerlijkheid' in Dutch or 'Seigneurie' in French) of Westerlo until the abolition of feudalism in 1795. The first known Lord of Westerlo was the Frankish nobleman Ansfried of Utrecht who gave this domain as allodial title to the chapters of Saint-Martin and Saint-Salvator in Utrecht after he became Bishop of Utrecht in 995. Since the late 15th century the Lords of Westerlo have been members of the House of Merode. In 1626 Westerlo was elevated to the rank of marquessate by King Philip IV of Spain in favor of Philippe I de Merode who became the first Marquess of Westerlo. The chief of the House of Merode still bears the title of Marquess of Westerlo although the feudal rights attached to this title have been abolished since 1795. In the nineteenth and first half of the twentieth century the 10th, 11th and 12th Marquess have been elected Burgomaster of Westerlo.