Why did millions of American farm families migrate westward from 1900 to 1910?

Western lands opened up for settlement--the end to Indian War and the passage of the Homestead Act opened new farm land.

New lands opened up after the end of the Indian Wars on the Plains in the 1870s and 1880s. Land could be purchased cheaply and new means of transportation made it easier for families to make the trip. New farming technology such as irrigation systems also made the land more manageable for farming.

The greatest expansion of farmland in the United States occurred in the Western State and the Plain States since 1900. Irrigation and harvest of crops increased during this period. Therefore, the American farm families migrated to the Western State.