Fascinating study of territories and national identities.
The Pyrenees boundary between France and Spain began in 1659 as a pretty arbitrary line, but over the course of the next two centuries it was worked out as a national border locally. Sahlins studied the Cerdanya, a valley in the Pyrenees split between France and Spain, and shows how localism formed national identities that were necessary fordelineating the boundary.

According to Sahlins, the changes that took place to form the
France/Spain boundary were not only a formation of national identity, but also a change in the governments' views of sovereignty, moving from an idea of jurisdiction and dominion over subjects, to territorial control. He shows how policy in the Cerdanya reflected this change from jurisdiction to territory, the change from frontier land to a true boundary.

Sahlins' book is a fascinating look at what makes a nation, and a
microcosmic study of the formation of the modern nation-state. His study of the Cerdanya gives the book insights, not just into
governmental state-building, but also the construction of identity,
the necessity of boundaries for people to define themselves in
opposition to the other.

"Boundaries: The Making of France and Spain in the Pyrenees"
Peter Sahins, University of California Press, 1991.

Catalan translation: "Fronteres i identitats: La formació d'Espanya i França a la Cerdanya, s. XVII-XIX", Eumo Ed., 1993.

There is a french translation.