History 24 Railroads 21 Street-railroads 21 Streets 13 Description and travel 12 Buildings, structures, etc 9 Transit systems 8 more ... Social life and customs 6 Transportation 6 Bus lines 5 Commerce 5 Buildings 4 Electric railroads 4 Underground Railroad 4 African Americans 3 Appropriations and expenditures 3 Architecture 3 Cars 3 Coal trade 3 Finance 3 Histoire 3 Local transit 3 Railroad stations 3 Suburbs 3 Subways 3 Buildings and structures 2 Centennial Exhibition (1876 : Philadelphia, Pa.) 2 Central business districts 2 Commuting traffic 2 Department stores 2 Directories 2 Harbor 2 Insurance companies--United States 2 Mayors--Pennsylvania--Philadelphia 2 Municipal officials and employees--Pennsylvania--Philadelphia 2 Philadelphia (Pa.)--City planning 2 Philadelphia Views--19th century 2 Railroads, Elevated 2 Slaughtering and slaughter-houses 2 Urban renewal--Pennsylvania--Philadelphia 2 less ...