The construction of the Argentine state unfolded within a political environment where provincial boundaries were formulated out of largely open frontiers.This paper seeks to explore this situation for the case of Corrientes and it rebuilt different positions and arguments about how boundaries must be defined during the second half past of 19th century, a period in which the province struggled (and failed) to incorporate the Missions territory under its jurisdiction.The analysis of various approaches to this questions permits a broader understanding of how Argentine politicians hoped to develop borderland spaces in more general terms and how the national Congress sometimes acted as referee or mediator among contending factions.