The Department of Native Affairs operated from January 1936 to 31 December 1954. It was preceded by the Aborigines Department. The Department of Native Affairs was continued by the Department of Native Welfare.
The State Records Office website provides an overview of the Department:
' In 1936, following the recommendation of the Moseley Royal Commission and the subsequent amendment of the Aborigines Act 1905, functions of the Aborigines Department were considerably increased and its name was at the same time changed to that of the Department of Native Affairs. In 1947, the portfolio of the Minister for Native Affairs was created and a year later the Bateman Survey recommended drastic changes in the organisation of the department. These changes were duly carried out in the following year.
In 1954, the name of the department was changed to the Department of Native Welfare and its duties and functions were laid down by the Native Administration Act of that year. '
The most useful doorway into records about Aboriginal history in WA is the SRO's 'Aboriginal Records' web resource, which is listed under 'publications'.