Coal has been a source of energy for almost as long as Homo sapiens have inhabited the planet. The earliest record for its use dates back more than 3000 years to China where it may have been used to smelt copper. In areas where coal seams intersected the surface, coal was a ready supply of energy just waiting to be exploited. It did have some drawbacks, though. Most of the coal near the surface burns dirty, requiring some form of chimney if it is to be used indoors. It is also heavy to transport, limiting its use to regions near the source. Because of this, the use of coal through history was fairly sporadic. There is evidence for its use in Iron Age Britain, as well as in Rome near the beginning of the Common Era. Its earliest use in the U.S. was in the 1300’s by Hopi Indians in the desert Southwest for cooking and potterymaking. With improvements in mining, transportation, and ventilation in Medieval Europe, coal use gained in popularity. However, it was not until the beginning of the Industrial Revolution that coal use really took off. Large-scale manufacturing and transportation required tremendous amounts of energy, the likes of which wood could never supply without very quickly denuding every forest in Europe. Coal also had the advantage of being able to be used to make coke, which is used to manufacture steel. The invention of the coal-powered steam engine by James Watt furthered the use of coal. It lead to the train and the creation of the steam–powered boat, which made possible the quick and reliable transport of the manufacturing plants goods to faraway locations. The timing of this revolution could not have been better for the U.S. from an economic standpoint. Coal had been discovered in the Colonies in the late 1600’s, and the first commercial mines began operation in the 1740’s. The plentiful supplies of this in places that were then Virginia and Pennsylvania helped the young country grow into an industrial powerhouse.