During the 1930s, a severe drought hit the great plains making it impossible to farm in most of the region. this event was known as the dust bowl. as a result of the dust bowl, many people moved from the great plains to

The correct example of California and the Western United States in general.

This is famously the story in many of John Steinbeck's works but the Graphs of Wrath in particular.

The influx of Dust Bowl refugees led to the explosion of California as a center in the US.