This paper argues that regions typically dubbed “tropical” or “sub-tropical” were often also inscribed as economic and agricultural resources. Specifically, it focuses on western European surveyors' descriptions of early twentieth-century Paraguay. In these texts, Paraguay was constructed as a series of fertile tropical and sub-tropical regions, easily harnessed by European capital. Moreover, to enable the appropriation of the myriad agricultural resources on offer, the surveyors indexed Paraguay's “development” to the progress of the railways, in turn portrayed as moral and altruistic ventures. The paper moves from a theoretical discussion of the construction of tropicality to a brief history of surveying. It then analyses the portrayal of Paraguay as a massive arena of tropical and sub-tropical goods, moving on to consider the role played by the railroads. The paper ends with a reflection on the relative successes of the proposed and actual schemes advocated by the surveyors in question.