As the demand for electricity and automobiles increased in
the 20th century, the world became dependent on oil. In the United
States, much of that oil came from foreign countries. But since two separate energy
crises in the 1970s, the U.S. has raced to become energy independent so it does
not have to rely on other countries for energy. That race has included the
search for domestic oil and gas, and the development of renewable energy.