Windmills, mechanisms that look like giant pinwheels, have been used to generate power and grind wheat since ancient times. American colonists used windmills to power machinery that could then grind wheat into flour and corn into cornmeal. Windmills also powered tools to saw wood and make typical household items, such as oil, paper, spices, chalk, and pottery. Through the 1920s, Americans used small windmills to generate electricity in rural areas. When power lines began to transport electricity to these areas in the 1930s, local windmills were used less and less, although they can still be seen in some parts of the western United States. When the oil shortages of the 1970s created an interest in alternative energy sources, windmills became fashionable again, especially in states like California whose governments encouraged renewable energy sources.
Today, clusters of giant windmills with blades up to 200 feet (61 meters) long sit atop windy hillsides in great numbers to make electricity. The force of the wind pushes the slanted blades, which causes them to rotate because they are bound by a shaft. This spinning shaft runs an electrical generator, which creates power. They are sometimes called wind power plants or wind farms. The world’s largest wind farm, the Horse Hollow Wind Energy Center in Texas, has 421 wind machines that generate enough electricity to power 230,000 homes per year. The states with the most wind production are California, Texas, Iowa, Minnesota, and Oklahoma.