HISTORY United States Presidents 17 BIOGRAPHY & AUTOBIOGRAPHY 11 History 11 American Civil War (1861-1865) 10 Military operations, Aerial 8 Jefferson, Thomas 7 World War, 1939-1945 7 American Revolution (1775-1783) 6 Politics and government 6 TECHNOLOGY & ENGINEERING 6 World War (1939-1945) 6 Lincoln, Abraham 5 Military campaigns 5 Reconstruction (U.S. history, 1865-1877) 5 Reconstruction (United States : 1865-1877) 5 Bombing, Aerial 4 Diplomatic relations 4 Generals 4 Military policy 4 RELIGION 4 Speeches, addresses, etc 4 USA 4 Abolitionists 3 Air power 3 Armed Forces 3 Grant, Ulysses S. 3 Great Britain 3 Persian Gulf War (1991) 3