John II Casimir Vasa
Old Łeba was threatened for many centuries by floods and expanding sand dunes and therefore was rebuilt in a safer location after 1558. The town was reintegrated with the Polish Crown after the death of the last Pomeranian duke Bogislaw XIV as part of the Pomeranian Voivodeship, until King John II Casimir Vasa enfeoffed Elector Frederick William I of Brandenburg-Prussia with Lauenburg Land by the 1657 Treaty of Bydgoszcz.