Arnsberg

The Counts of Arnsberg grew out of the Counts of Werl, who moved their seat to a castle above the Ruhr at Arnsberg around 1080. When the old Werl line died out in the twelfth century, the county passed through the heiress Jutta to Godfrey I of the House of Cuyk.

Hemmed in by Mark and Cologne, his successors lost Rietberg to a kinsman in 1237 and cleared forests and founded towns in the Sauerland. In 1337 Count William ruled, followed by his son Godfrey IV, while a younger son of the house, Godfrey of Arnsberg, served as Bishop of Osnabrück from 1321 to 1349.

As Godfrey IV remained childless, he sold the county to the Archdiocese of Cologne in 1368; its lands became the core of the Cologne Duchy of Westphalia, and the Arnsberg eagle entered Westphalia's arms.