The essays collected in this volume explore the frontier theme in American history, not only as it relates to issues of political jurisdiction, territorial expansion, and cultural interaction, but also as a concept which is applicable to any different types of historically significant boundaries that have been used to differentiate and separate, that have been renegotiated, or that might be historiographically redefined. Physical geography, demographic movements, international relations, political culture, social customs, language, religion, and other cultural factors, as they intertwined over time, have all played roles in the historical processes of defining the nation, its values and the limits of its power. The same factors have also given rise to different social groups, interests and jurisdictions within the nation. These essays examine many kinds of frontiers and boundaries -- territorial, economic, ethnic, literary, artistic, ideological, political, institutional, administrative, and even historiographical -- discussing theoretical and interpretative problems in their demarcation, as well as their transgression, and their relationship with the exercise of power, from colonial times to the present.