Politics and government Territorial expansion History 59 Imperialism 19 Political aspects 16 Foreign relations 13 Slavery 13 more ... Extension to the territories 11 Frontier and pioneer life 9 Political culture 8 Race relations 8 Government relations 7 Nationalism 7 Indians of North America 6 National characteristics, American 6 Colonies 5 Democracy 5 International relations 5 Manifest Destiny 5 Relations 5 Diplomatic relations 4 Influence 4 Louisiana Purchase 4 Philosophy 4 Annexation to the United States 3 Constitutional history 3 Constitutional law 3 Missouri compromise 3 Racism 3 Sectionalism (United States) 3 less ...