Territorial expansion History 28 Foreign relations 13 Frontier and pioneer life 12 Imperialism 7 Indigenous peoples 7 Politics and government 7 more ... Race relations 5 Historiography 4 Colonies 3 Description and travel 3 Frontier and pioneer life in literature 3 Influence 3 Manifest Destiny 3 National characteristics, American 3 Colonial question 2 Culture conflict 2 Discovery and exploration 2 Filibusters 2 First contact with other peoples 2 Frontier thesis 2 History and criticism 2 Louisiana Purchase 2 Pioneers 2 Political aspects 2 Political culture 2 Public opinion 2 Racism 2 Republicanism 2 Slavery 2 less ...