Roads 110 History 75 Harbors 54 Historical geography 28 Cartography 19 Population 11 Maps 10 Geography 9 Social indicators 8 Economic indicators 7 Economic conditions 6 Economic development 6 Environmental indicators 6 Geographical distribution 6 Discovery and exploration 5 Gross national product 5 Politics and government 5 Slave trade 5 Civilization 4 Geology 4 Social conditions 4 World War, 1939-1945 4 World maps 4 World politics 4 Antiquities 3 Campaigns 3 Cities and towns 3 Dicotyledons 3 Election 3 Elections 3 Gettysburg, Battle of, Gettysburg, Pa., 1863 3 Identification 3 Maps as Topic 3 Medical care 3 Medical geography 3 Nautical charts 3 Presidents 3 Social aspects 3 Statistics 3 Voting 3 Agriculture 2 Botany 2 City planning 2 Climatic changes 2 Cold War 2 Description and travel 2 Dialects 2 Discoveries in geography 2 Diseases 2 Early maps 2 Early works to 1800 2 Emigration and immigration 2 Environmental conditions 2 Floodplains 2 Floods 2 Food supply 2 Galaxies 2 Geographical perception 2 Geography, Medieval 2 Geological mapping 2 Grasses 2 History of Biblical events 2 History, Ancient 2 Human geography 2 Indians of North America 2 Industries 2 Languages 2 Linguistic geography 2 Methodology 2 Names, Personal 2 Natural disasters 2 Phytogeography 2 Political campaigns 2 Psychological aspects 2 Public health 2 Railroads 2 Religions 2 Research 2 Slavery 2 Urbanization 2 AIDS (Disease) 1 Administrative and political divisions 1 Advertising 1 Aerial photography in watershed management 1 Age Groups 1 Alliances 1 Analytical, Diagnostic and Therapeutic Techniques and Equipment 1 Anatomy 1 Anthropology, Education, Sociology and Social Phenomena 1 Anti-apartheid movements 1 Apartheid 1 Arabic language 1 Architecture 1 Art 1 Atlases 1 Atlases as Topic 1 Attitudes 1 Authors, English 1 Aztecs 1 Balance of power 1