The first written mention of Kalush can be found in the municipal register of Halicz (Halych). The entry is dated 27 May 1437 and refers to the “court hearing on the first Tuesday after St. Trinity’s Day with the participation of royal burgher, Dragusz of Kalush, against Mytek of Kurosz.” The name of the town probably comes from the word for a place where salt was extracted.

Situated on the bank of the Sivka River (tributary of the Dniester), Kalush had the status of a village until 1549, when King Zygmunt August authorised the Governor of Bielsko and Alderman of Halicz, Crown Hetman Mikołaj Sieniawski, to found the town of Kalush. The town was chartered under Magdeburg Law.

In the 15th century, Kalush was experienced a period of swift development. It was known for salt mining, brewing and malt production. The Alderman of Kalush was the father of King Jan III Sobieski – Jakub Sobieski (1590-1646). An important role in the history of Kalush was played by Duke August Aleksander Czartoryski (1697-1782), who not only serves as the Alderman of Kalush but also as the Provincial Governor of Ruthenia, the Alderman of Podolia, and the commander of the Polish army in 1729.

After the First Partition of Poland in 1772, Kalush came under Austrian rule. In the interwar period, it was part of the Polish territory. Salt production was thriving at the time thanks to the activities of the Salt Exploitation Society based in Lviv.