sentences:  In 1637 the last duke of Pomerania Bogislaw XIV died, the House of Griffin became extinct and the duchy ceased to exist.Usedom was annexed by Sweden after the war for almost a century, until in 1720 it was sold for 2 million thalers to Prussian King Frederick William I.In 1740 Frederick the Great of Prussia developed a seaport in Świnoujście (then "Swinemünde").