Agnes Milne was the second female factory inspector to be appointed in Adelaide and in this article I explore how she redefined the parameters of factory inspection by infusing the role with a radical agenda. Through a consideration of Milne’s activism, we can see how she politicised the position of factory inspection. I argue that Milne acted as a trade union advocate and radical social reformer in her capacity as inspector. This article also situates the factory inspector within the emerging practice during the late nineteenth and early twentieth century of the creation of certain classifications and categories which have been termed ‘political arithmetic’. Through an examination of Milne’s activities we can see how factory inspectors paradoxically used similar techniques of classification and observation — often associated with social control — to argue for the regulation of working hours and improved conditions on behalf of the working classes.