Tariff 23 Protectionism 21 History 19 Politics and government 13 Causes 9 Political parties 9 Canals 8 more ... Plague 7 Yellow fever 7 Public works 6 Railroads 6 Banks and banking 5 Foreign relations 4 Histoire 4 Poles in the United States 4 Polish people 4 Commercial policy 3 Disease Outbreaks 3 Education 3 Fièvre jaune 3 Mortality 3 Politique et gouvernement 3 Poor 3 Publishers and publishing 3 Yellow Fever 3 African Americans 2 Agriculture 2 Atlases 2 Child welfare 2 Colonization 2 Commerce 2 Conditions économiques 2 Description and travel 2 Diplomatic relations 2 Economic conditions 2 Economic history 2 Emigration and immigration 2 Epidemics 2 Industrial promotion 2 Mortalité 2 less ...