Caption: Some of the nearly 5,000 wind turbines at Altamont Pass in California
A windmill is a machine that uses wind energy to make mechanical energy. People have used windmills to do work for more than a thousand years. Early windmills often had four or five blades covered with cloth sails to catch the wind. Windmills were used to pump water, grind corn, and saw lumber.
In 1890, a windmill pumped water to make electricity for the first time. Soon, nearly six million windmills made electricity in the United States. Then large power companies began using oil to make less costly electricity. The windmills were taken down.
In the 1970s, supplies of oil ran short. The cost of oil and other types of fuel went up. People had to find a way to make electricity and run machines without using oil. Scientists and engineers began to work on the problem of energy.