[citation needed] The first written record of Haapsalu dates back to 1279, when the town was chartered and became the capital of the Bishopric of Ösel-Wiek, which it remained for the following three centuries.

Buildings from those early days remain today, including an episcopal castle, which has the largest single-nave church in Estonia.

News of the "curative mud" spread quickly amongst the wealthy customers in then capital city Saint Petersburg, and elsewhere in the former Russian Empire.

[5] In 2017, the pastors of Haapsalu made an open statement calling to end the city's financing of the festival, claiming the horror and violence depicted in the screened films were not fit to represent the resort town image.

[7] Pyotr Ilyich Tchaikovsky in 1867 wrote a suite of three pieces for piano during his stay in Haapsalu, titled Souvenir de Hapsal.