The present article proposes an analysis of the elements that structure the inequalities in local youth policies by referring to the notion of local system of public action. Based on an analysis in political sociology, it brings together empirical data from historical material and from four research programmes conducted over the last ten years. These data focus on various fieldwork studies and different periods of time, allowing to go beyond the simple description of local particularities and to identify the elements of local systems of public action. By referring to the analysis of this notion, the present article aims to put into perspective and to explain the territorial specificities in the implementation of youth policies, going further than the simple assertion of the contingency of public initiatives. In doing so, it proposes a typology of local systems of public action that focus on the articulation of their elements (the historical legacy, the seriousness of local situations, the roles of the various actors and the impact of their networks) and demonstrates how these local systems may be changing according to periods, places and issues.