Territorial expansion History 120 Imperialism 42 Foreign relations 40 Politics and government 27 Frontier and pioneer life 22 Political aspects 15 more ... Manifest Destiny 12 Race relations 11 Colonies 10 Historiography 10 Relations 10 Slavery 10 Indians of North America 9 Racism 9 Discovery and exploration 8 National characteristics, American 8 Government relations 7 Indigenous peoples 7 Influence 7 Political messianism 7 Social aspects 7 Extension to the territories 6 Louisiana Purchase 6 Political culture 6 Public opinion 6 Civilization 5 Colonial question 5 Nationalism 5 Philosophy 5 less ...