<P> 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 . </P> <P> 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 . </P> <P> Carnegie's great innovation was in the cheap and efficient mass production of steel rails for railroad lines . This could not have happened without the prior invention of Bessemer Steel . Thus Carnegie's "innovation" was scale, not anything technical . </P> <P> In the late 1880s, The Carnegie Steel was the largest manufacturer of pig iron, steel rails, and coke in the world, with a capacity to produce approximately 2,000 tons of pig iron per day . In 1888, he bought the rival Homestead Steel Works, which included an extensive plant served by tributary coal and iron fields, a 425 - mile (685 km) long railway, and a line of lake steamships . A consolidation of Carnegie's assets and those of his associates occurred in 1892 with the launching of the Carnegie Steel Company . </P>

Where did the south's iron and steel industry develop