Nearly a century later, in 1521, these two duchies, along with the county of Ravensberg, fell extinct, with only the last duke's daughter Maria von Geldern left to inherit; under Salic law, women could only hold property through a husband or guardian, so the territories passed to her husband—and distant relative—John III, Duke of Cleves and Mark as a result of their strategic marriage in 1509.

These united duchies controlled most of the present-day North Rhine-Westphalia that was not within the ecclesiastical territories of Electoral Cologne and Münster.

The Privilegium Unionis had declared that the Duchies of Jülich, Cleves, and Berg would remain united rather than divided during succession.

The situation was further complicated by acquisitive desires of Emperor Rudolph II and the Wettin dukes of Saxony—the former particularly worrying to Henry IV of France and the Dutch Republic, who feared any strengthening of the Habsburg Netherlands.

In 1701, the Margrave-Electors of Brandenburg became Kings in Prussia; with Cleves-Mark as their first possession in western Germany, it was the seed of the future Prussian Rhineland.