The article analyzes three Brazilian expeditions to Western Amazon whose mission was to demarcate the boundary between Brazil and Bolivia during the years 1895-1901. The goal is to seize the role of science in a negotiation that gave to Brazil its actual territorial shape. In the point of view of history of science, the paper deals with a traditional topic of geopolitics - the formation of international borders - highlighting the intersection between institutionalization of science and the construction of nation.
Scientific expedition; Territory; History of Astronomy; Acre; Brazil; Bolivia