A windmill is a machine that converts the energy of wind into rotational energy by means of vanes called blades, used in the western United States and elsewhere to pump water for livestock. Maintenance is extensive, although the "power" is clean and free. In desert country water is life. Often water, not feed, is the limiting factor for livestock and wildlife. Ranchers, by developing water sources, improve the range for both. As you can see in some of the photos, in places windmills have been replaced by solar panels or gas or diesel engines to power the pumps.