[1] The Neman River (Lithuanian: Nemunas) supplies about 90% of its inflows; its watershed consists of about 100,450 square kilometres in Lithuania and Russia's Kaliningrad Oblast.

In 1454, King Casimir IV Jagiellon incorporated the region to the Kingdom of Poland upon the request of the anti-Teutonic Prussian Confederation.

[3] Following the peace treaty of 1466, the lagoon became a part of Poland as a fief held by the Teutonic Knights,[4] and thus located within the Polish–Lithuanian union, later elevated to the Polish–Lithuanian Commonwealth.

After 1923, the Klaipėda Region in the north passed to Lithuania (occupied by Germany in 1939–45), whereas the remainder fell to the Soviet Union following World War II.

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.