Although child labor has been nearly eradicated in rich countries, it remains pervasive in the developing world. Recent estimates indicate that 215 million children between the ages of 5 and 17 are working in some form of child labor. Of those children, 53% are engaged in work defined as hazardous, or “likely to harm [their] health, safety, and morals.” Given that children don’t vote or participate in politics, they have no political recourse to advocate for their own rights or interests. Aside from the obvious normative and welfare implications, child labor may have important consequences for economic development. Children who work sometimes do so at the expense of schooling. Given the proposed link between investment in human capital and economic growth and poverty alleviation, child work should be taken seriously as a potential bottleneck to development. To date, most academic work aimed at understanding child labor has been done by economists. Economists (unsurprisingly) attribute child labor patterns primarily to economic factors, and the link between child labor and poverty is fairly well-understood. However, comparatively little has been done to understand the politics of child labor. Activists and child welfare advocates frequently implicate the state, arguing that governments ought to do more to protect the interests of child workers. Without knowing more about the constraints and incentives of governments, however, it is difficult to understand the opportunities for and limitations of state action. Under what conditions do governments intervene on behalf of the rights of child workers? Child labor activists use ethical arguments about child welfare to advocate for state protection of child workers, but skeptics argue that these humanitarian ideas have little power in the face of economic interests in keeping cheap child labor available.The 1833 Factory Act is credited as the world’s first piece of child labor legislation with any enforcement clout. It was passed at the height of the Industrial Revolution, when child labor was cheap, readily available, and still being used widely in the textile industry, which was a major engine of growth in British economic development. Despite the fact that the legislation was bitterly opposed by the powerful industrial class, and despite the fact that members of the government had an economic interest in keeping their economy productive for the purpose of taxation and geopolitical competition, they nevertheless passed legislation that effectively imposed a tax on one of the industry’s key inputs, child labor. A simple model based on economic interests would not predict this outcome. What explains the introduction of laws against child labor at precisely a time when it made little economic sense to do so?This paper considers the following question: since the economic interests of powerful societal groups fail to account for the outcome of child labor law during the British Industrial Revolution, what explains it? Ultimately I consider the relative contribution of economic interests, political incentives, and ideational factors in the adoption of the 1833 Factory Act.The puzzle of child labor law has relevance for a larger theoretical question, of interest to those who study institutions as well as those with development or humanitarian goals: Under what conditions do humanitarian considerations (such as minority protection, human rights, or labor rights) get institutionalized into rules when they run contrary to materialist incentives of powerful societal groups? What is the power of ideas about rights in the face of materialist interests? Is discourse about humanitarianism merely rhetorical window-dressing for the unfolding of political and economic interests, or do ideational factors have real influence in protecting the rights of marginalized groups?This paper is a hypothesis-generating case study. It includes a detailed case history of the birth of child labor law in England. This paper does not make a systematic attempt to quantify its conclusions – I leave that to future work. The aim here is to present qualitative evidence from the first case of child labor law and situate it in political and historical context in order to elucidate why and how political elites legally restricted child labor during a period when the employment of children was contributing significantly to the productivity of a key British industry and was economically profitable to an increasingly powerful class of industrialists.