Statistiques de la population et politique des catégories aux États-Unis au xixe siècle. Théories raciales et questions de population dans le recensement américain.

The American census, taken every ten years since 1790, was created by the Constitution to apportion the seats of Representatives in proportion of the population of the States. Therefore, Congress maintained a firm control on the questions asked, and the political dimension of the census was important. Looking at three cases, I show how the census was located at the intersection of different levels of action, political, scientific and technical; the results fed the debates, and conversely, census categories were also constructed in relation to the political context. The treatment of the insanity statistics of free blacks in 1840, the creation of the mulatto category in 1850 in order to maintain mixed-race individuals inside the population defined as black and in the hope of documenting the degeneracy of the “hybrids”, and finally the attempt, starting in 1870, to define the offspring of immigrants by inherited traits and not just by place of birth, show how political questions of population were also conceived in biological terms.