The observatory was built thanks to the initiative of the commercial executive Reginald Czermack-Warteck, who was a meritorious member of the presidency of the Mountain Association in Teplice and chairman of the mountain associations of northwestern Bohemia. Scientific commission for the construction of the observatory was headed by the university professor Dr. R. Spitaler. E. Hoka’s design was selected on February 25, 1903 from five projects submitted by various architects.
The construction of the observatory began in the spring of 1903. The basic building material was the phonolite, which was mined directly at the top of Milešovka. The construction was completed in June 1904. Part of the observatory building is an 18 m high tower; at 10 m the observation deck is situated. Meteorological observations and measurements have been taking place here continuously since 1905 (with a short break in 1917 and during World War II). A continuous series of meteorological records is one of the longest in the Czech Republic; Milešovka is the oldest mountain observatory in the Czech Republic.
The first director of the observatory was prof. Rudolf Spitaler, Head of the Department of Space Physics and Geodynamics at the German University in Prague. He held this function until February 1929. In 1953, the observatory came under the administration of the Czechoslovak Academy of Sciences (ČSAV), first it was part of the Institute of Geophysics, later of the Laboratory of Meteorology and in 1964 it passed to the Institute of Atmospheric Physics. In 2005, significant repair work was carried out on Milešovka (insulation, repair of the facade, renovation of the interior, etc.).