This article studies the process of the configuration of census statistics in the first half of the 20th century in Colombia. It indicates the singularities of the production and uses of these figures, and describes the problems that the Colombian state faced in producing scientifically reliable demographic statistics, as an imperative of modernity. Analysis of the documentation showed that the censuses of 1905, 1912 and 1918 aimed mainly to quantify the male population who had the right to vote and were fit for military service. It also showed the administrative weakness of the official statistics services and the participation of international experts in the elaboration of subsequent censuses.