Drawing upon the example of 20th century French geography, the paper argues that the production of knowledge on nations and national territories by geographers is significantly influenced by how geographers are embedded within national institutions when producing this knowledge. More specifically, the paper shows how the conflation of the nation state as a category of knowledge and as a category of action and the interaction of the various "modes of existence of space'' according to which the idea of nation has been seized have indeed deeply shaped French geography both at the beginning and at the end of the 20th century.