QUOTE : Americans mined two kinds of coal: soft, sooty bituminous, about 60 percent to 70 percent carbon; and clean, hard anthracite, 92 percent to 98 percent carbon. Because of its impurities, bituminous coal smoked; anthracite burned clean. The one anthracite region known in the United States before smaller fields opened in Colorado and New Mexico lay in eastern Pennsylvania. Once the residents of eastern cities learned how to burn anthracite in their fireplaces—it needed a raised grate to provide a draft to keep it burning—they were willing to pay a premium for the hard coal. The coal trade that developed in the eastern United States between 1820 and 1860 was predominately anthracite.