While it's uncertain who specifically invented the windmill, the earliest windmills known to exist were used by the Persians in A.D. 500 to A.D. 900 and by the Chinese in A.D. 1200. These early windmills were used to power grain mills and water pumps.
The first windmills built in the United States were manufactured by Daniel Halladay, who started building them in his machine shop in Connecticut in 1854. These windmills were widely popular, especially in the agriculture industry, and they aided in the westward expansion of the United States. Windmills also played a key part in the development of the railroad industry where large amounts of water were needed to help fuel the steam-driven locomotives.