History Politics and government Race relations 6 Extension to the territories 4 Slavery 4 Territorial expansion 4 Political aspects 3 more ... Social conditions 3 African American women journalists 2 African Americans 2 Agriculture and politics 2 Antislavery movements 2 Frontier and pioneer life 2 Frontier thesis 2 Indians of North America 2 Influence 2 Land use 2 National characteristics, American 2 Parks 2 Political messianism 2 Populism 2 Right-wing extremists 2 White supremacy movements 2 Anti-imperialist movements 1 Chinese 1 Conservatism 1 Diplomatic relations 1 Elections 1 Emigration and immigration 1 Equality 1 less ...