The main point of the discord between Brazil and Argentina, but mainly, on the part of Argentina, was accurately this river, whose passage was unknown in 1750. But that already it appeared in the Treat one to Madrid, as being the point that delimited the border between Brazil and Argentina in the region of the Territory of the Missions. This river, later, in 1759, the Portuguese and Spanish, in charge commissioners of landmarks in this year, after having recognized, and explored the Pepiri, had gone down the unknown river, tributary of the Iguau, which had given to the name of River Saint Antonio; he corresponded this to the express determination in the Treated one to 1750. Regarding the controversy, around the localization of the River Saint Antonio, stranger in 1750, D' AMARAL, 2003, p.110, observes the following one: the strategy of defense of Rio Branco, with regard to the question of the Missions, was very simple, but very laborious: to find the map that the accurate position of the Peperi Rivers proved conclusive, or Pequeri and Santo Antonio. continuing its comment, it says: this map existed outside done in 1749 to guide the Treat one to 1750. It was the map of the Cuts.
Of it two copies were only known: of Borges de Castro, favorable to Brazil, and the Frenchman, where, modified the positions of the rivers, related above, it attended reason Argentina. She was necessary, therefore, to find the original. This the knot of the question. After clarified, the main reasons of the dispute Argentine-Brazilian regarding the Territory of the Missions; it is important to point in this brief paragraph, that Rio Branco, was not since the beginning to the front of the negotiations with regard to the question of the Missions. Before exactly to go Washington to present it President Cleveland, had obtains (Rio Branco), a good amount of documents favorable to Brazil.