For the French, mid-nineteenth-century Mexico remained a virtual unknown. Thus the French expeditionary force sent by Napoleon III was charged with not only drafting new accurate maps of the Mexican territory and preparing geographic accounts of its provinces, but also emphasizing its economic and demographic potential. As a result, the military archives of Vincennes in Paris, contain an important number of unpublished documents that afford us a completely new approach to the views of the French towards Mexican'realities' of that period, and also of relations between France and the USA.