Beginning in 1935 intensive efforts were made by both federal and state governments to develop adequate programs for soil conservation and for rehabilitation of the Dust Bowl. The measures taken have included seeding large areas in grass; 3-year rotation of wheat and sorghum and of lying fallow; the introduction of contour plowing, terracing, and strip planting; and, in areas of greater rainfall, the planting of long shelter belts of trees to break the force of the wind. Dry spells in the 1950s, 60s, and late 70s were responsible for recurrences of dust storms in the region.
In the 1930s and 1940s, the region also received two waves of major migrations: that of farm families from the southern Great Plains migrating west to escape the Dust Bowl, and that of African Americans moving out of the American South. During World War II the need for labor, especially in ship and aircraft production, boosted the population even more. The population of Los Angeles County jumped from 3 million to 4.7 million between 1940 and 1950.
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