Define "Migrant."

Are you specifically referring to Mexicans / other nationalities south of the border?

Because by some definitions you could have just about anyone who moved- there was a lot of this- being classified as a "migrant worker." Incidentally, if you haven't seen Ken Burns' documentary on Depression era mid-west you absolutely should since it does a fantastic job of capturing the spirit of the era.

Otherwise nationality and / or region of the US becomes very important. Someone who happened to be in California is going to experience something entirely different than, say, Oklahoma.