Sopot was originally founded in the 13th century, with earthen forts, and was a fishing village but lost most of its fortunes early on with the founding of a Ducal fort in Gdansk around the same time.
In the 17th and 18th centuries, Sopot became renowned for its spas.
Due in part to a napoleonic era doctor promoting Sopot, Jean Haffner, the city grew to include many spas, a sanatarium, and public baths.
Even after being burned to ruins in the 18th century by Russian troops, Sopot retained its reputation and an affluent resort town, and the Emperor of Prussia, Wilhelm II, owned a villa and a summerhouse (The Maryla and Magnolia Hotels).
For even more curious observers, we offer the following links:
Stay Poland history site of towns in Poland: http://www.staypoland.com/
Sopot 2014 English site: http://www.sopot2014.com/en