This dissertation examines the first piece of comprehensive public health legislation in New Zealand, the 1872 Public Health Act. Previous historians of New Zealand public health have downplayed the significance of the Act, and nineteenth century public health measures in general, suggesting the Act was poorly implemented by Health Boards who had little interest in their duties. This dissertation tests these claims by examining the implementation of the Act in Auckland Province, focusing on Auckland City and its suburbs, where most of the Local Boards of Health were. To fully understand this topic, a number of aspects of public health at the time and of the Act itself are investigated. Wider aspects of public health covered include health conditions in Auckland during the period, and how far they changed, and beliefs and ideas about public health that were held. This dissertation also discusses how the Act was formed in the context of such ideas and conditions, which aspects of it were actively pursued, which were neglected, and by whom, and how far there was a will to act that was limited by factors such as lack of funding, resources and knowledge. These subjects are examined through the use of a range of sources, including official government records, Board of Health records, statistics and newspapers, paying attention to both the substantive information that can be gained from such sources, as well as their discursive elements. This dissertation examines the different levels of power and responsibility set up by the section of the Act which created the Boards of Health, recognising that while there were not always tangible results, there was often an expressed will to act by public health authorities. This dissertation concludes that the Act was an important development in New Zealand's public health history, providing the first legislative expression of the 'sanitary idea' and setting up structures of responsibility that placed much more power to define sanitary conditions with public health authorities than hitherto existed, reducing the ability of individuals to do so and creating a 'new politics of health' that represented a new era.