Go to the library and sign out books about farm windmills. Check the "Windmill World" bibliography for a comprehensive list of books and additional resources, such as a videos.
Study diagrams of how farm windmills work. Make a time-line of the height and decline of farm windmills in America. Juxtapose this with a map showing the areas that had the highest concentration of farm windmills.
Contact the American Windy Energy Association. This lobby group promotes the use of wind energy because it is economic and environmentally friendly. Ask them for resources about farm windmills and inquire how many farmers continue to use them.
Interview a farmer about the windmills he has on the farm. Prepare questions ahead of time, such as how they were built, what are were used for and whether they supply enough electricity for the farm, or if he had to supplement it with power from the line.
Visit a farm and see a windmill in action. The best way to learn about windmills is to do it in person. When you go on this field trip, take the sketches you made of how it works and compare what you thought with the real thing.
Check out the YouTube clips on farm windmills. If you can't get to a farm, this is the next-best option to learn more about windmills, because it allows you to see farm windmills in operation on the Internet.