Doc,
I grew up in southern CA in a rich agricultural valley during the bracero era. The workers "only" were allowed to come over and work the fields. They lived in camps provided by the farmer. They were allowed to stay for 6 months and then had to go home. I stood in line at the Post Office or the check cashing cage at my market many times behind a bracero while he bought a money order to be sent home to his family in Mexico.
This was a good program, for the farmer and for the worker. The program was discontinued around 1964 by congress. After that the inflow of illegals ramped up. They saw how good the life was in the US and started coming over in droves with their families.
This is an out of control problem for ICE now.