https://en.wikipedia.org/wiki/Arenberg
1826. In 1826, the Arenberg territory in Hanover was named the duchy of Arenberg-Meppen, and it had an area of 2,195 km² and a population of 56,700. The county of Recklinghausen, in Prussia, had an area of 780 km² and a population of 64,700. The Dukes of Arenberg remain a prominent Belgian aristocratic family.