This paper is derived from the authors' detailed studies of two groups of nineteenth-century families—eighteen families in Argentina and twenty-four in Chile. The studies revealed such remarkable similarities in the evolution of the two groups that it is possible to propose a broad generalization in respect to the social organization and national formation of both countries: there was, in each country, a three-generation sequence during which a number of families came together to form clusters that became the controlling entities of a region. Their base for political and economic control was either the existing capital city or a city that had been designated as the capital by these families.