The Spanish Royal Crown administration collaborated with international experts in the 19th century to produce a pioneering set of forestry maps. Forestry held a privileged place in cameralist thought and had material characteristics that were amenable to standardized classification. Analysis of this project revealed very clearly how national and international communities of experts generated knowledge about the Spanish territory. Producing credible environmental knowledge at that time required an international network of disciplined experts, and the Royal Corps of Forestry Engineers saw forestry maps as a way of producing a new community of experts. The map colors and legends corresponded to a new international classification system and constituted a groundbreaking accomplishment because of their potential to unify Spanish administration practices. The rigorously empirical descriptions of trees also revealed the interplay of the cosmopolitan values of scientific internationalism with the social tensions of that century.