As the new interwar border, the river that flows into the Curonian Lagoon near Rusnė was chosen. The river's lower 120 km in Germany were called die Memel by Germans, while the upper part located in Lithuania was known as Nemunas River. The border also separated the peninsula near the small holiday resort of Nida, Lithuania. From 1939 to 1945, the Lithuanian part was occupied by Germany, and the southern part of the Spit and the Lagoon remained in Germany until 1945.
This border is now the border between Lithuania and Russia, as after World War II, the southern end of the Spit and the German area south of the river became part an exclave of Russia called Kaliningrad Oblast.
The nearly extinct ethnic group the Kursenieki lived in the surrounding area.