United States History 39 Politics and government 32 Biography 24 Foreign relations 17 Terrorism 11 Presidents 10 World War, 1939-1945 9 September 11 Terrorist Attacks, 2001 7 War on terrorism, 2001- 7 Prevention 6 Soldiers 6 Sources 6 Intelligence service 5 Social aspects 5 Social conditions 5 Causes 4 Civil rights 4 Personal narratives, American 4 Revolution, 1775-1783 4 Vietnamese Conflict, 1961-1975 4 Antislavery movements 3 Civil War, 1861-1865 3 Civilization 3 Cold War 3 Decision making 3 Ethics 3 Influence 3 Iraq War, 2003 3 National security 3