text: From 1875 to 1920 American steel production grew from 380,000 tons to 60 million tons annually, making the U.S. the world leader. The annual growth rates in steel 1870–1913 were 7.0% for the US; 1.0% for Britain; 6.0% for Germany; and 4.3% for France, Belgium, and Russia, the other major producers. This explosive American growth rested on solid technological foundations and the continuous rapid expansion of urban infrastructures, office buildings, factories, railroads, bridges and other sectors that increasingly demanded steel. The use of steel in automobiles and household appliances came in the 20th century.
  Some key elements in the growth of steel production included the easy availability of iron ore, and coal. Iron ore of fair quality was abundant in the eastern states, but the Lake Superior region contained huge deposits of exceedingly rich ore; the Marquette Iron Range was discovered in 1844; operations began in 1846. Other ranges were opened by 1910, including the Menominee, Gogebic, Vermilion, Cuyuna, and, greatest of all, (in 1892) the Mesabi range in Minnesota. This iron ore was shipped through the Great Lakes to ports such as Chicago, Detroit, Cleveland, Erie and Buffalo for shipment by rail to the steel mills.  Abundant coal was available in Pennsylvania, West Virginia, and Ohio. Manpower was short.  Few Native Americans wanted to work in the mills, but immigrants from Britain and Germany (and later from Eastern Europe) arrived in great numbers.
  In 1869 iron was already a major industry, accounting for 6.6% of manufacturing employment and 7.8% of manufacturing output. By then the central figure was Andrew Carnegie, who made Pittsburgh the center of the industry.  He sold his operations to US Steel in 1901, which became the world's largest steel corporation for decades.
  In the 1880s, the transition from wrought iron puddling to mass-produced Bessemer steel greatly increased worker productivity.  Highly skilled workers remained essential, but the average level of skill declined.  Nevertheless, steelworkers earned much more than ironworkers despite their fewer skills.  Workers in an integrated, synchronized mass production environment wielded greater strategic power, for the greater cost of mistakes bolstered workers' status.  The experience demonstrated that the new technology did not decrease worker bargaining leverage by creating an interchangeable, unskilled workforce.