At the outbreak of World War I, Tončić had the ethnographic collection stored away in patriots' houses and in the Art Gallery building, preventing so the Viennese Government from transferring the collection to Graz, Austria. After the War the collection was brought back into the Craft School building and in 1919 it was transferred again to Agricultural School near Archaeological Museum. The display rooms, though larger than the previous ones, were again cluttered with numerous exhibits.
Having acquired ethnographic material originating from a broader area, the Museum became a regional one. In 1923 Tončić deeded the Museum to the City of Split which would hereafter provide financial means for the Museum's activities. Tončić was appointed director of the institution.
The following year (1924) another building became the site of the Museum - former City Hall at the National Square. However, only in 1927 was the Museum officially founded, and its Regulations passed by the Municipal Assembly.
Around the paintings and other works of art selected from the Museum's holdings in the late 1920s, the permanent collection of Art Gallery would be built at 11 Lovretska Street in 1931.
The Museum's display was changed in 1934 and lasted till the beginning of World War II. The photographs of the display, taken after 1931, serve as evidence of the galleries being cluttered with objects, just like the galleries in the School building, which were described by Tončić in 1913. There were so many exhibits in the showcases, which had been designed by Tončić himself, that it was often not possible to view an object as a whole.
During World War II the permanent collection was exposed to danger of being transferred to Rome, but Tončić again succeeded in frustrating such plans of the authorities.