Real property 83 Maps 51 History 25 Railroads 22 Description and travel 21 Canals 6 Coal mines and mining 6 more ... Travel 6 Anthracite coal 5 Election districts 5 Central business districts 4 Social life and customs 4 Streets 4 Atlas 3 Coal reserves 3 Coal trade 3 Early works to 1850 3 Finance 3 Geology 3 Histoire 3 Natural history 3 Outlet stores 3 Railroad 3 Roads 3 Street-railroads 3 Appropriations and expenditures 2 Art galleries, Commercial 2 Canaux 2 Cartography 2 Centers for the performing arts 2 Coal 2 Colonies 2 Descriptions et voyages 2 Geography 2 Geology, Stratigraphic 2 Historic districts 2 Indians of North America 2 Internal improvements 2 Languages 2 Location 2 less ...