starting in the mid-nineteenth century, there is a legislative basis for the health of housing first and then a definition of assisted housing (Melun law on public health in 1850; Siegfried Act on cheap houses in 1894). According to Jean-Claude Perrot, “the invention of the urban issue by a century surrounds that of the social question”: if the 18th century had looked in space for explanations of urban pathology, the 19th century would have focused on understanding social problems in urban areas. Since the end of the 19th century, the scale of social conflicts has shifted social concerns to the issue of housing. And hygiene would be at the heart of this process, from medical to social hygiene (Perrot, 1975). On the government side, change took place from 1896 with the arrival of new political forces (Socialists and left-wing radicals) in the municipal government, leading, locally, to the implementation of social policies (city-gardens) and the strengthening of urban legislation at national level (Strauss Act in 1906; Bonnevay Act in 1912; Cornudet Act in 1919). These frameworks have served as instrumental fields for urban planning conditioned by the means, forms and techniques of early public intervention. They also explain the integration of housing into urban policies under development, with left-wing mayors having some competences in urban matters and not in housing. Lastly, after taking a century to move away from charitable policies towards poverty in favour of a general concept of prevention, the State (in its contemporary acceptance) took over urban and housing policies from the 1940s onwards, and confines this public action from a highly centralised perspective, under the characteristics of a ministry in construction. In addition, although engineers took over the equipment aspect of the territory through infrastructure, they remained more out of the city’s sphere and the housing issue (despite the strong involvement of some structural and road engineers, especially those who were sensitive to the speeches of the Social Museum). Splitting into three parts: —The years 1850-1894: this period is politically dominated by the Second Empire (Napoleon III having been Prince President during the Second Republic) and is marked by awareness of the need to transform urban areas, mainly in the name of hygienism (in the restrictive sense of public health and revolutionary danger). The issue of housing is relegated to the back plane and/or in the hands of the private sphere — charitable and especially industrial companies. The Habitats Act in Bon Market, passed in 1894, accentuates this phenomenon by emphasising the private nature of this issue. during this period, the urban issue becomes a public policy that integrates the issue of housing. First of all, the work of local authorities (identified by the name of municipal authorities), this issue is ‘centralising’ under the effects of the two wars. The Courant Plan, adopted in 1953, illustrates this process. In the years 1954-1969, planning and rationalisation are being implemented in urban policies. In a context of modernisation in France, there is an unprecedented movement in the massive policy of assisted housing, along the lines of the SPAs (urban areas to be developed by priority) and then large groups. The leadership of engineers will also guide the technical and “equipping” vision of the urban issue. However, at the end of the 1960s, this type of urban action was lost.