Territorial expansion History 43 Foreign relations 23 Imperialism 16 Civilization 6 Colonies 6 Indians of North America 6 Frontier and pioneer life 5 Government relations 5 Manifest Destiny 5 Social aspects 4 Discoveries in geography 3 Racism 3 Anti-imperialist movements 2 Boundaries 2 Campaigns 2 Colonization 2 Economic integration 2 European influences 2 Exceptionalism 2 Filibusters 2 First contact with Europeans 2 Indians, Treatment of 2 Land tenure 2 Mexican War, 1846-1848 2 Military relations 2 National characteristics, American 2 Philosophy 2 Political and social views 2 Political aspects 2