Between 1900 and 1935, the Argentine economy experienced important changes. Strongly specialized at first in the exportation of primary goods to European markets, the economy gradually turned to import substitution for the internal market. This transition was accompanied by increases in the number and scope of the functions performed by the State. In this paper we approach this evolution with an analysis of public investment in two critical areas: railways and water and drainage works, both of which resulted in the formation of the first public enterprises. Other aspects of public finances are also examined here: the evolution and structure of tax collection and public debt, both of which experienced an ever increasing complexity and scope.