Arnsberg

Arnsberg was a county in the Sauerland between the Ruhr and Möhne, centred on the castle and town of Arnsberg. Its counts faced the expanding archbishopric of Cologne and County of Mark.

With no heir, Count Gottfried IV sold the county to Cologne in 1368. Arnsberg became a centre of Cologne's Duchy of Westphalia and in 1437 received the Vehmic court transferred from Dortmund. After the Napoleonic upheaval, it passed to Prussia in 1815 and became an administrative centre of Westphalia.