Various rationales have been advanced to explain the phenomenon of corporate social reporting. Among these has been legitimacy theory which posits that corporate disclosures are made as reactions to environmental factors and in order to legitimise corporate actions. This paper reports the results of an historical analysis of social disclosures in 100 years of annual reporting by a dominant corporation in the Australian mining/manufacturing industry. A variable but significant pattern of social reporting is identified and compared with an earlier study of social reporting by US Steel. The results of this study fail to confirm legitimacy theory as the primary explanation for social reporting in the Australian case.