The development of the iron industry was an indispensable but highly localized component of industrialization. For all of its precocious mechanical developments before the Civil War, the United States still lagged behind Britain in metallurgical industries. But the country was fast catching up and would quickly adopt Bessemer steel methods after the war. In Mastering Iron, Anne Kelly Knowles provides the best explanation we have about why the U.S. lagged in making iron for so long and how it overcame much of its backwardness by the Civil War.

The book begins by characterizing the antebellum U.S. iron industry using a survey of iron-making establishments through 1858 commissioned by the American Iron Association, which includes the establishment date, products, location, materials source, and technology of working and abandoned firms. Knowles supplemented these with other data and established the exact location of plants with GIS methods. The resulting data set is the best available on the structure, evolution, and— as depicted in a series of excellent maps—the geography of the antebellum industry. The data demonstrate the great variety of the industry, varying by fuel source (charcoal, bituminous coal, anthracite coal, all with different impurities), iron ore quality, production methods (hot vs. cold blast; water vs. steam power), scale, location, and markets. There was some decline of firms that were smaller and used older methods—charcoal fuel, cold-blast technology, water power—but the decline was slow and the diversity of the industry persisted through the Civil War. Knowles identifies distinct regions, of which the region around Philadelphia had the biggest share of large, integrated mills. An interesting section points to how labor relations differed between various types of rural and urban firms.

U.S. firms tried to adopt leading British techniques (including, prominently, Welsh and Scottish methods), but with mixed success and a long period of catching up. Knowles addresses the sources of failure and success largely through well-chosen and nicely researched case studies. She identifies several factors leading to failure. First, the geography of iron production inhibited industry development because sources of iron ore were often distant from sources of coal, and because production, located near iron ore, was distant from markets. Second, the chemistry of American ores and coal differed from those of Britain, entailing risk and requiring learning. Third, though most efforts involved recruiting and learning from British immigrants, the quality of such instruction was hard to determine, outmigration from isolated rural locations was great, managerial capabilities were often limited, and problem-solving skills were lacking. Finally, many firms, particularly outside cities, were isolated from international networks of iron practitioners. The South felt these limits acutely during the Civil War.

Yet some American firms did succeed. Success came principally in the mid-Atlantic region surrounding Philadelphia, which possessed a fuel source similar to those used in Britain, trained artisans and managers, proximity to markets and resources, and good transportation. As the insightful study of the Lehigh Crane Iron Works demonstrates, success required sustained access to technological knowledge. The company was formed when its owners used international networks to learn of a Welsh technique to form pig iron with anthracite using a hot blast, licensed patents rights, and recruited a key innovator and ironmaker, David Thomas, to build and manage the factory. He recruited Welsh workers and succeeded quickly. He then introduced technical improvements and trained workers who spread knowledge to other firms in the region and to firms in Pittsburgh and even the South. As Knowles shows, network linkages at Lehigh Crane and other firms were critical to success, and their cumulative effects enabled expanded output in the North during the Civil War and the quick adoption of the Bessemer converter to mass produce steel shortly after the war. Hence the antebellum iron industry created conditions and agents for the great upsurge of mass-produced steel of the late nineteenth century.

The explanation of the structure and evolution of the iron industry could have been more complete if the book addressed other issues. It would have been useful to characterize the structure of firms more precisely, indicating the roles of owners, superintendents, foremen, and skilled workers and their importance for worker training and mobility. Did the sort of collective knowledge sharing that Robert Allen documents for the Cleveland region of England exist in the Philadelphia or Pittsburgh regions? Patent data might have traced the spread of invention through assignments and documented the rise of secondary inventions.

Still, more than any other book, Mastering Iron has identified the diversity and trajectory of the U.S. iron industry as it overcame its backwardness and was poised for ongoing development in the steel age. It belongs on a short list of leading books on the emergence and development of the U.S. iron and steel history into the early twentieth century along with Peter Temin's Iron and Steel in Nineteenth-Century America, Robert Gordon's American Iron, and Thomas Misa's A Nation of Steel. That's a real accomplishment.