The city's history is complicated. The Port of Klaipėda is important in the area. It is a usually ice-free port on the Baltic Sea. It has been controlled by the Teutonic Knights, the Duchy of Prussia, the Kingdom of Prussia, the German Empire, the Entente States, Lithuania, and the Third Reich. The city became part of Lithuania while it was a Soviet Socialist Republic. Klaipėda remained part of Lithuania after it again became independent state.