This article looks into the voyage of the "royal escort", a reconnaissance expedition sent from Belém do Pará in 1749 to explore the fluvial communication between the state of Maranhão and Grão-Pará and the captaincy of Mato Grosso down the courses of the Rivers Madeira, Mamoré and Guaporé, and its impact on the cartographic representation of this region. The considerable differences between the map drawn by José Gonçalves da Fonseca and the map of the boundaries of Brazil prepared for the negotiations with the Spanish Crown astonished the Portuguese politicians in charge of the matter before they set out to demarcate the South American territories according to the Treaty of Madrid signed by Portugal and Spain in 1750.
Maps; Boundaries; River courses; Mato Grosso; Madeira River; Treaty of Madrid
