International borders are usefully conceptualized as international political institutions that provide joint gains for the polities whose jurisdictions they distinguish. Far from irrelevant in an age of globalization, settled political borders help to make economic integration possible. But the international relations literature that focuses on territorial disputes has put too much emphasis on territory per se and far too little on the institutions of boundary settlement that produce joint gains. Students of international politics have cast the issues relating to territorial settlement in overly zero–sum terms, and may very well be missing an important impetus to conflict resolution in many cases. This paper shows empirically for the case of Latin America that territorial and border disputes entail opportunity costs (operationalized here as bilateral trade foregone). Mutually accepted borders mitigate these costs by reducing uncertainty, transactions costs, and other bilateral externalities of disputing. Theories of territorial settlement should take into account the possibility of such joint gains in their models of state dispute behavior.