The town dates back to 1279, when it was chartered and became the centre of the Bishopric of Osel-Wiek, which it remained for the next 300 years. Buildings from those early days remain today, including an Episcopal castle which has the largest single-nave cathedral in the Baltic states, Haapsalu Castle.
For many years, locals have claimed that the sea mud has a curative effect. A military doctor, Carl Abraham Hunnius, founded the first mud cure resort in 1825. News of the curative mud quickly reached the aristocracy of Saint Petersburg, the capital of the Russian Empire. Ever since then, Haapsalu has been a popular summer destination where people from all around the world come for medical treatment. Today, there are three mud cure establishments in Haapsalu varying in size and location.
Haapsalu and the surrounding area was the center for the Swedish population in Estonia from the 13th century until the evacuation of almost all ethnic Swedes from Estonia in 1944.
In the 19th century, Haapsalu became famous for its shawls, a delicate craft made by local women. The Land of Ilon Wikland (Wiklandia), a recreation centre for children, is set to open in a few years within the town. This world famous book illustrator has been involved with Haapsalu since her childhood. The August Blues Festival is held every August in Haapsalu.
During the Cold War, Haapsalu Air Base, southwest of the town, was home to an interceptor aircraft regiment
