Between the 1848 War and the first decade of the Twenty Century, Sonora?s history was marked by three fundamental events. The first one was the railroad construction inside the Mexican territory led by Americans. The second one, resulting as a consequence of the railroad links, was the rise of the mine production, focused on industrial metals, particularly cooper. This fact brought on the increasing presence and eventual predominance of American markets and capital in the State. Although such openness towards the USA transformed Sonora in one of the richest states of Mexico, it also sealed its dependency upon the Northern Neighbour. Finally, due to the increasing importance of the American markets and American investments, the retook place an economic growth pattern that favored those localities more closely tied to the USA at the expense of others. This essay tells part of this history.