1930s - The Dust Bowl
The decade 1930 brought incredible drought years, intensifying a phenomenon that was already common in the mid-west of the United States - dust storms. Though the most intense drought years were 1934 and 1936, the most severe dust storms were in 1935, with 40 in that year, and 1938, with a whopping 61 in that year.
Once the protective covering of the native grassland had been destroyed, plowed for the planting of crops, the topsoil was more susceptible to wind erosion, a reality made worse by dry conditions and the high winds that were common to the region. It has been estimated that by 1938, 5 inches of topsoil had been lost over an area of 10 million acres and 2.5 inches of topsoil 13.5 million acres due to wind erosion. The most severely affected locations were in Oklahoma (in Cimarron, Texas and Beaver counties), Texas panhandles, western Kansas, eastern Colorado and northeastern New Mexico.
D.A. Wilhite, The Encyclopedia of Oklahoma History and Culture, s.v. "Dust Bowl",