The dynamic development of Szczawnica dates back to the mid-19th century.
In 1857, Józef Dietl arrived to Szczawnica; he was a physician and promoter of Polish spas, and he outlined the development strategy for the Szczawnica resort. New spa houses and guesthouses were erected then. Also, some new thermal springs were discovered.
In 1909, Szczawnica was acquired by Adam Stadnicki of Nawojowa. His actions, even though undertaken during the economically difficult period of the world wars, led to further development of Szczawnica. Most of the spa houses were refurbished, the Górny Park was extended to include the area of the Polonyna (Carpathian meadows used mainly as pastures), an inhalatorium was built, equipped with pneumatic chambers for inhalations, which were then unique in Poland. The luxurious ‘Willa Pod Modrzewiami’ (’Villa under the Larches’) was built.
The outbreak of the Second World War stopped the development of the resort.
1948 - the communist authorities nationalised the spa.
1956 - the Państwowe Przedsiębiorstwo Uzdrowisko Szczawnica (State Enterprise Szczawnica Spa) was established. The sanatorium activity was mainly focussed on treatment of occupational diseases affecting coal-miners and steelworkers. So-called industrial sanatoria began to be built, among others Hutnik (Steelworker), Górnik (Miner), later on also other, Nauczyciel (Teacher), Budowlani (Construction Workers), Papiernik (Papermaker), Dzwonkówka (the name refers to a nearby mountain) and Nawigator (Navigator).
2001 - heirs of Count Adam Stadnicki filed a petition to the Ministry of Health annulment of the decision of March 1948 concerning nationalisation of the spa.
2005 - the Polish government returned the Szczawnica spa to the heirs of the pre-war owners, who undertook to restore the resort through numerous investments as well as projects promoting the resort at home and abroad. Recently, Andrzej Mańkowski, grandson of Count Adam Stadnicki, together with his wife decided to engage financial resources in order to restore the former splendour and charm to Szczawnica, the place that has always been close to their hearts. For the fulfilment of these objectives, the Thermaleo has been established.