It holds the "South Australiana" collection, which documents South Australia from pre-European settlement to the present day, as well as general reference material in a wide range of formats, including digital, film, sound and video recordings, photographs, and microfiche.

On 29 August 1834, a couple of weeks after the passing of the South Australia Act 1834 by the British parliament,[1] a London-based group led by the Colonial Secretary, Robert Gouger, and solicitor Richard Hanson[2] and a number of prominent colonists, including Ernest Giles, Edward Gibbon Wakefield, John Morphett, Robert Torrens Snr, and John Hindmarsh, formed the South Australian Literary Association at the city's Adelphi Chambers.

[3] Within a month, the title was changed to the more inclusive South Australian Literary and Scientific Association[1] with the aim of "the cultivation and diffusion of useful knowledge throughout the colony".

This Act also ensured the library would be open to the public free of charge, and granted funding was allocated to it.

)[9] The Public Library, Museum and Art Gallery Act 1884 renamed the South Australian Institute as Public Library, Museum and Art Gallery, and also broadened the scope of the Board's control to include the expanding network of regional and suburban institutes.

The library has also acquired over 100,000 images by renowned local aerial photographer Douglas Darian Smith, as well as film memorabilia from filmmaker Scott Hicks' personal archive.

[15] The building now known as the Mortlock Wing was opened on 18 December 1884 as a "Public Library, Museum and Art Gallery for the colony of South Australia" with 23,000 books and a staff of three.

)[16] The foundation stone was laid on 7 November 1879 by Sir William Jervois and the building was constructed by Brown and Thompson at a total cost of £36,395, and opened in 1884.

The walls are constructed of brick with Sydney freestone facings with decorations in the darker shade of Manoora stone.

The balconies feature wrought iron balustrading ornamented with gold while the glass-domed roof allows the chamber to be lit with natural light.

Two of the original gas "sunburner" lamps survive in the office space located on the second floor at the southern end.

After the State Library underwent a substantial redevelopment, commencing in 2001 and reaching completion in 2004, the main chamber of the Mortlock Wing became an exhibition space providing a glimpse into the history and culture of South Australia.

In August 2014 the Mortlock Wing featured in a list of the top 20 most beautiful libraries of the world, compiled by the U.S. magazine Travel + Leisure.

The State Library has a national responsibility to collect, preserve and give access to historical and contemporary South Australian information.

The York Gate Library was acquired from the estate of Stephen William Silver, of S. W. Silver and Co. (William) a London-based company who not only sold clothing, furniture and equipment suitable for emigrants to the British Colonies, but also a series books providing relevant information for such emigrants.

The Children's Literature Research Collection was formed in 1959 and has over 65,000 books, periodicals, comics, board and table games, and toys.

The Library manages, in collaboration with the History Trust of South Australia, the Centre of Democracy on the corner of North Terrace and Kintore Avenue.

[25] The Centre's gallery exhibits treasures from History Trust and State Library collections, as well as items on loan from State Records of South Australia, the Art Gallery of South Australia, the Courts Authority, Parliament House, Government House and private lenders.