The effective southern border of Spanish control emerged early in the sixteenth century with the creations of a series of small scattered postas (forts) linking the early colonial settlements of Buenos Aires, San Luis, Mendoza, Santiago, and Concepción. This frontier changed very little in the sixteenth, seventeenth, eighteenth, and early nineteenth centuries. The relative autonomy of native societies south of this frontier was assured over the centuries in part because apart from small outposts that served the needs of passing ships, like Puerto Deseado (Carmen de Patagones) on the Atlantic coast and Valdivia and Chiloe on the Pacific coast, the Spanish presence in the Southern Cone was minimal after 1600 until the nineteenth century. Most of the Spanish activities and resources were oriented to the north to support the mining industry. However, the initial negotiations over this frontier between Spanish conquistadors and the native people they encountered in the early colonial period resulted in reorganization and adaptations among Indian societies that allowed them to maintain political sovereignty well into the late 1800s. That native peoples numbering at least between 100,000 to 300,000 individuals were able to resist conquest and colonization for nearly four centuries deserves our attention when considering the history of South America.

We are accustomed to imagining the political boundaries of the Spanish empire in the southern cone of South America as following the north–south axis of the Andes, extending to the tip of Tierra del Fuego. We can see this north–south orientation projected in the historical mapping of colonial and national political boundaries as they were increasingly subdivided and defined over the centuries. By the twentieth century this political process ultimately resulted in the (still disputed) establishment of the national border of over 2,000 miles dividing the countries of Chile and Argentina.

The first task inherent in understanding interethnic reorganization and readaptation at the margins of Spanish rule is to challenge that north–south perspective and to imagine instead an east–west (or west–east) boundary. Nearly all of the territory south of this boundary – roughly defined by the military outposts linking the colonial settlements of Buenos Aires, San Luis, Mendoza, Santiago, and Concepción – remained free of Spanish colonial rule. With the exception of a few heavily defended Spanish outposts along the Atlantic and Pacific coasts, native peoples claimed and enjoyed sovereignty in this vast region known as Patagonia by the Europeans.