From its origins, when Public Health was integral to societies'' social structures, through the Sanitary Movement and Contagion eras, when it evolved as a separate discipline, to the "New Public Health" era, when Population Health and revised Primary Health Care concepts appear to be navigating public health back to its roots as a Social Justice movement built on a scientific base, public health seems to have come full circle. Based on 23 years of public health practice as well as extensive literature review, the author examines seven previous public health eras in relation to their dominant paradigms, action framework and legacies. The emerging era of Population Health-New Primary Health Care is also analysed in terms of its distinctive conceptual framework and potential for achieving a core objective of Public Health: Social Justice.