How many dust storms occurred in the Southern Great Plains during the 1930s? Why is that significant?

Roughly 2.5 million people left the Dust Bowl states—Texas, New Mexico, Colorado, Nebraska, Kansas and Oklahoma—during the 1930s. It was one of the largest migrations in American history. Oklahoma alone lost 440,000 people to migration. Many of them, poverty-stricken, traveled west looking for work

answer; european crusades;