If you're talking about the FSA (Farmer Security Administration) of the 1930's it was part of the OWI - a movement started by the government to complement the "New Deal". Basically, they were trying to get people back to work, and producing crops to be able to feed America during, and after the depression. Roy Stryker was given the task of hiring photographers to help spin the effort by documenting the move west.
Some of the more notable photographers that came out of this time were:
Ben Shahn
Dorothea Lange
Paul Taylor
Walker Evans
Margaret Bourke-White
If you look into the Library of Congress' Web site, look under FSA/OWI, migrant workers, tenant farmers, and the dust bowl - you'll find much of what you're looking for.
HTH's
Art Gardiner