All but untouched by Europeans until the 1880s and officially under Bolivian jurisdiction before 1903, Acre is Brazil's final frontier. Housing a third of its population is Rio Branco, founded in 1882 by enterprising settlers who saw in Acre the perfect climate for rubber tree cultivation. These settlers, soon joined by hundreds of others from Brazil and Bolivia, enslaved thousands of natives in their lust for latex, becoming the 'Rubber Barons' that dominate Acre to this day. When Bolivia began policing the territory, the barons revolted, and in 1903 secured incorporation into Brazil. Rio Branco's small size belies its enormous importance, with Japan restricting American and German access to the rubber of Southeast Asia, Rio Branco is of the utmost importance to militaries and carmakers the world over.