Despite our contined reliance on wood, as new forms of energy were developed throughout our nation's history, the mix of fuels used to power homes, businesses and our economy changed over time, which the animation above shows. Wood served as the primary form of energy until about 1885, when it was surpassed by coal. Despite rapid expansion, coal use was in turn overtaken by petroleum and natural gas in the 1950s. Then, in the second half of the 20th century, natural gas use increased quickly, and we began developing nuclear electric power and renewable energy. Using clean energy sources including renewables like wind, solar and biofuels supports hundreds of thousands of jobs, increases energy efficiency and helps shrink our nation’s carbon footprint. In fact, our economy today is 60 percent bigger than it was 20 years ago, while our carbon emissions are roughly back to where they were 20 years ago.