What is the role and importance of a political parties in our political system? Why does the United States have a two party system instead of a multiparty system, like most other advanced democracies?

What has been the impact of third parties and why have there been so few effective third parties in our history?

I believe the answer is:

The migrants worked in the fruit picking industries

The climates in california enable various varieties of fruits to grow and attract more than a million immigrants to come and work in the fruit picking industries. The term 'okies' were used in a derogatory manners because it sounded like an animal or a pet name.