Rietberg

The counts of Rietberg ruled an imperial county on the upper Ems in Westphalia, between Paderborn and Muenster. Centred on the castle above Rietberg, it emerged as an independent county in 1237, with its own militia, laws and coinage. In 1456 Count Conrad V had to surrender immediacy and hold it as a fief of the landgraves of Hesse for 600 Rhenish guilders.

The Reformation was introduced in 1535 under Otto III, but the county was later re-Catholicized. The male line ended when John II died in prison in Cologne in 1562; his daughters were enfeoffed in 1565, and Walburgis married Enno III of East Frisia in 1581, carrying Rietberg to his house.

The East Frisian house's Rietberg line failed in 1690. In 1699 heiress Maria Ernestine married Maximilian Ulrich von Kaunitz, founding Kaunitz-Rietberg. Mediatized to Westphalia in 1807, the county passed to Prussia in 1815.