At the beginning of the twentieth century, as steel production became more dependent on the use of electric arc furnace technology in mini-mill environments, the convenient transportation of scrap metal became a competitive advantage of manufacturers, so the availability of geographical resources was no longer the most significant driving force for iron-and-steel production growth. The Birmingham area began to invest in building the earliest mini-mills, and continued to have a strong foundry emphasis, attracting many large cast-iron pipe producers, such as American Cast Iron Pipe Company. Headquartered in Birmingham in 1905, American Cast Iron Pipe Company, with its 2,100 acre site and 2,400 employees at its operations, became the worlds largest iron pipe casting plant. With advanced expertise and the latest technological innovations, Birmingham furnaces produced millions of tons of pig iron from 1990s to 1970s. A half of the produced pig iron was used for steel production, and the other half was sold as foundry iron. This trend reflected that the regions iron ore was of poor quality, so manufacturers had difficulties in extracting it. This is a geological factor that limited the further development of Alabama's iron and steel industry, despite the help of advanced technology and innovative smelting practices.