Kajaani was one of the cities founded in 1651 by the Governor General of Finland, Per Brahe. At that time, the Kainuu region—as wood country—was an important producer of tar derived from pine, and the tar trade was its major industry. The barrels of tar were shipped to Oulujärvi and then along Oulujoki to Oulu on the Bothnian coast of the Baltic sea. From there, tar was shipped to continental Europe, where it was used as a sealant and an anti-rot agent for ship hulls.
One famous historical monument in Kajaani is the ruins of Kajaani Castle, located on an island in River Kajaani in the centre of the city. The castle was originally built in 1604 and completed in 1666. The castle served as an administrative centre, prison, military base and a refuge for the citizens.
During the Greater Wrath in the 18th century the castle was forced to surrender to Russian forces. The Russians blew the castle up in March 1716 and it has been in ruins ever since. Today, the ruins are especially popular among children who like to explore the dark, twisty little passages and have fantasy adventures.
In the beginning of 20th century Kajaani industrialized step by step and the city begun growing especially after a railroad connection southward to Iisalmi and further to Helsinki and St Petersburg was established. The growth of population was strongest just after the Second World War. The population has been decreasing since mid-1990s.
In 1977 the separate rural municipality of Kajaani, Kajaanin maalaiskunta, and Kajaani were consolidated to form the City of Kajaani. The town, in addition to railroad and road connections, is served by a Finnair-operated air connection to Helsinki, during the summer twice daily and three times a day during the winter schedule period. Kajaani Airport, located in the Paltaniemi area, close to central Kajaani, is maintained and operated by Finavia, also serving the needs of non-commercial general aviation.
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