France's demographic transition occurred a century before any other country's. We test Le Play's hypothesis that this demographic transition was triggered by the harmonization of inheritance practices after the French Revolution. After a series of laws implemented in 1793, the Loi de Nivôse, year II, imposed the equality principle, effectively abolishing impartible inheritance practices that excluded non-heirs from inheriting. In regions that moved from impartible to partible inheritance, we expect fertility to decline if parents face a quantity-quality tradeoff. In regions that removed the exclusion of women, we expect fertility to decline because of women's empowerment and delay in marriage ages. To test these hypotheses, we compile a harmonized map of inheritance practices before the French Revolution at a highly disaggregate level. To estimate the effect of these inheritance practices on fertility, we use genealogical data and exploit the 1793 harmonization in a difference-in-differences framework. (joint with Marc Goñi and Victor Gay).