The booklet, intended for students and other visitors to the Lathrop E. Smith Environmental Education Center (Rockville, Maryland), explains how windmills work and their economic and environmental advantages. The history of windmills in Europe and Asia is briefly described, as well as the history of windmills and wind generators (for electricity) in America. The windmills at the Smith Center (an American multi-bladed wind pumper, an 1800-watt wind generator, and a 200-watt wind generator) are explained and illustrated. Factors affecting windmill performance, such as wind speed, tower height, and tower location, are covered. Economic and environmental advantages of wind power are detailed. Additional sources of information are listed: six books, two periodicals, two agencies, and four films. A 13-item glossary is provided. (MH)