Sortavala's first architecturally significant commercial building was the Leander building, developed by Magistrate J.O. Leander on a plot in his ownership in the corner of Karjalankatu and Koulukatu between 1904 and 1905. The design for the building, representing romantic nationalism, was produced in 1903 in the architect firm Gesellius-Lindgren-Saarinen. The facade was designed by Eliel Saarinen, but the floor plans and sections were probably designed by J.O. Leander himself. The first floor of the Leander building contained business premises, and the second floor was reserved for apartments. When digging foundations for the building, a previously unknown species of rock was discovered and given the name sortavalite. Locally sourced rock was also used in the building itself: the low footing was made of granite blocks quarried in Riekkalansaari island. The same rock was also used in the main entrance of the building together with dark red gneiss-granite from Kirjavanlahti.
Eliel Saarinen becoming the designer of the Leander building was connected to the Kansallis-Osake-Pankki bank that from 1901 onwards operated in the old wooden Leander house located on the same site. The bank manager was Eliel's brother Hannes Saarinen. The operations of the bank were moved to the new building in 1905. Hannes Saarinen was the manager of Kansallis-Osake-Pankki from 1901 to 1911. In 1913, the post was given to Oski Leander (1873–1942), who between 1893 and 1903 had designed more than 200 buildings and alterations in Sortavala and also acted as fire inspector from the 1890s onwards. The Bank of Finland also operated in the Leander building, but in 1915 it moved to a separate building designed by Uno Ullberg, and its old premises were occupied by Karjalan Rauta Osakeyhtiö, established in 1917.