Iron industry and trade 170 History 108 Iron and steel workers 36 Steel industry and trade 30 Iron mines and mining 19 Iron-works 19 Iron 17 more ... Iron foundries 16 Coal mines and mining 12 Iron industry and trade--Pennsylvania 10 Ironwork 9 Labor unions 9 Railroads 9 Cast-iron 8 Economic conditions 8 Wrought-iron 8 Equipment and supplies 7 Tariff 7 Biography 6 Building 6 Building, Iron and steel 6 Histoire 6 Iron ores 6 Blast furnaces 5 Fer 5 Industries 5 Labor and laboring classes 5 Social conditions 5 Anthracite coal 4 Businessmen 4 Description and travel 4 Forge shops 4 Furnaces 4 German Americans 4 Glass manufacture 4 Historic sites 4 Iron Manufacturing--19th century 4 Iron founding 4 Iron industry 4 Metallurgy 4 less ...