Here's a short clip from Hearst's Metrotone newsreels for MGM about the ban California placed on penniless people moving to California. The idea was that people like that would be a charge on the state. If you're familiar with THE GRAPES OF WRATH in any form, you'll recognize the situation.
Interestingly, thirty years later, when Chavez began to unionize the migratory workers, the farm owners who opposed his efforts vehemently were often Okies who had moved to California despite the ban. I am not certain how the state action ended, but the current state of law holds that American citizens have the right to travel from one state to another without let or hindrance; if they are driving autos or trucks, though, they do need a valid driver's license.