In the process of building the Brazilian Imperial State, which began in 1822, Pedro I, established in Rio de Janeiro, acted to submit almost half of the territory of the former Kingdom of Brazil under his rule. Thus, the article will analyze the Empire's actions to establish its southern border on the R & iacute;o de La Plata, considering how the southern limits were influenced by the Emperor's penniless, as well as the direction of the war in Brazilian Northern. Finally, the relevance of the naval forces for the implementation of Rio de Janeiro's imperial project of controlling the territory situated from Amazonas to Prata will be analyzed.