The former Treasury Building was built in stages from 1839 to 1907. The buildings we see today took nearly twenty years to reach completion, though their unity of conception suggests that they were designed as a whole by E. A. Hamilton who was Colonial Architect at the time when it was begun and who supervised the erection of the three earliest sections. The northern two-storied section of the Treasury Building in King William Street was built in 1858, followed by the corner two-storied section in 1859, and the central three-storied King William Street section in 1860. In 1867 the two-storied eastern Victoria Square section was completed. Finally in 1876 the three-storied Victoria Square block completed the structure. In order to make that possible a one-storied office building erected about 1842 to the design of Sir George Kingston, architect, was demolished. No doubt the design of that now forgotten Kingston building to some extent affected the general design, although this stuccoed pile with its urn-capped parapets is reminiscent of Nash’s terraces in Regent’s Park, London.
When the goldfields of Victoria opened up in 1851, some 17,000 South Australians left their homes and employment to seek riches in the east. Many who made their fortunes returned to South Australia and invested in land.
Meanwhile others took advantage of the Bullion Act of 1852 by selling gold in Adelaide at a higher price than was being offered on the diggings. This was made possible by the pioneering of a gold escort route from Mount Alexander, Bendigo, and Ballarat to Adelaide by Alexander Tolmer, South Australian Inspector of Mounted Police. During these escorts some 327,000 ounces of gold was brought to Adelaide without loss through wild lonely country inhabited by bushrangers. The escorts were welcomed by large crowds in the quadrangle of the Treasury Building on the north-east corner of Victoria Square.
The Treasury stood at the centre of South Australia’s administrative and governmental affairs for more 130 years. It housed the Cabinet Room from 1876 until 1968. The building has a strong association with exploration and surveying the sale and management of land the development of the State’s agricultural and pastoral industries and executive government. The building has now been restored and redeveloped as Medina Grand Hotel. The National Trust runs tours of the old Cabinet Room and tunnels under the building used for the secure transport of gold.