The largest is Karsibór island, once part of Usedom, now separated by the Piast Canal dug in the late 19th century to facilitate ship access to Szczecin.

Świnoujście directly borders the German seaside resort of Ahlbeck on Usedom, connected by a street and 12 km (7 mi) of beach promenade.

Since 1999, Świnoujście has been a city with powiat rights (Polish: miasto na prawach powiatu), within West Pomeranian Voivodeship.

In later centuries, local Pomeranian princes ruled the area, and on both sides of the river, they built fortified castles, which were destroyed by the Danish invasions in 1170 and 1173.

In 1297, Duke Bogusław IV granted merchants who entered through Świna protection and exemption from customs duties on the return journey, and most of the larger cities of Pomerania were eventually granted full exemption from customs duties on the Świna, yet the local castle was still destroyed by the city of Szczecin in 1457.

Świnoujście (Swinemünde) was founded on the site of Westswine in 1748, fortified, and received town privileges from King Frederick II of Prussia in 1765.

The town had broad, unpaved streets and one-story houses built in the Dutch style, which gave it an almost rustic appearance.

The river mouth, which was the entrance to the harbor and regarded as the best on the Prussian Baltic coast, was then protected by two curving long breakwaters, and was strongly fortified.

During World War II, Germany operated a forced labour subcamp of the Stalag II-D prisoner-of-war camp in the city.

The unfinished German aircraft carrier Graf Zeppelin was scuttled in the harbor in an attempt to prevent its capture by the advancing Red Army (it was nevertheless refloated by the Soviets later).

After Germany's defeat in the war, the Allied Nations imposed new borders in Central and Eastern Europe at the Potsdam Conference, which made the area, including Świnoujście, part of Poland, with a Soviet-installed communist regime, which stayed in power until the Fall of Communism in the 1980s.

In another trial, the town's chief of police, Jan Zientara, was sentenced to eight years, for organizing robberies of German civilians.

The construction of a large fish farm began, a huge swimming pool and industrial buildings were built, and three years later the Fisheries Base was commissioned.

[12] It was not until 27 November 1950, that the GDR government agreed to transfer to Poland the water intake for the city of Świnoujście, located at Lake Wolgastsee and demarcating the border there again.

Currently Uzdrowisko Świnoujście S.A. belongs to the largest and most modern in Poland, and its greatest asset is still bromide-iodide-sodium brine discovered a hundred years ago.

The city is located on the Strait of Świna, which in its northern part connects with the Baltic Sea, and in the south with the Szczecin Lagoon.

Land border controls were abolished 21 December 2007, and free automobile traffic to and from Germany was allowed for the first time since 1945, as Poland implemented the Schengen Agreement.