IntroductionAmerica is built on available energyThere is nothing wrong with America except faith, love of liberty, intelligence and energy of its citizens cannot heal Dwight D. EisenhowerAmerican general and Republican politician (1890 - 1969)When President Eisenhower said these words. I don't imagine he would have imagined the critical role energy plays in 21st century America. Everywhere we look, energy is being transformed and consumed. Our cars need it. Our emails to family use it. The strawberries we eat in Wisconsin got here, thanks to the energy used in transportation systems. America has always thrived on abundant energy. Early American Energy Sources Many pre-Revolutionary portraits show famous people standing near a fireplace. Wood was an abundant source of energy in pre-Revolutionary years in America. Trees were freely available in the early years of our country. In the 1600s, 1700s, and 1800s, wood was by far the dominant energy source, but coal was increasingly used. But, as scientists delved deeper into the sources of energy and matter, in 1776 Cavendish discovered hydrogen. His experiments isolated this most fundamental element, paving the way for increased use of hydrogen in the 21st century. Energy Sources of the 1900s In the first half of the century, coal became the dominant energy source in America. During the 1900s, when the population increased four-fold, energy consumption increased 10-fold. Oil energy consumption increased significantly and became the dominant energy source by the end of the century. By the end of the century, energy consumption in the United States had quadrupled compared to the 1800s. This was due in part to the increase in the American population, but mainly to the need for societal changes brought about by the First and Second World Wars. Energy sources of the 2000sAt the start of the 21st century, petroleum energy remains the dominant energy source. And, due to the changing nature of our industries, natural gas has become a much more common source of energy than coal or wood. But hydrogen is a growing energy resource. What is hydrogen? The name hydrogen comes from the Greek language: Hydro: water, genes: formation. As we noted earlier, Henry Cavendish is credited with isolating pure hydrogen and defining some of its key properties. Some of these properties include that it is: Colorless, odorless, non-metallic, univalent, highly flammable, diatomic gas. It is the most abundant element in the universe..