Photographer Dorothea Lange was working for the Resettlement (Farm Security) Administration in March 1936 when she drove past a sign for a pea pickers’ camp along Highway 101 near Nipomo, California. She stopped and snapped some photographs. Her description for the series of six images read: "Nipomo, Calif. Mar. 1936. Migrant agricultural worker's family. Seven hungry children. Mother aged 32, the father is a native Californian. Destitute in a pea pickers camp, because of the failure of the early pea crop. These people had just sold their tent in order to buy food. Most of the 2,500 people in this camp were destitute."
Lange didn’t ask for the woman’s name and even though the photograph almost instantly became a national icon, nobody knew the identity of the woman or her children until she came forward in a defiant interview with the Modesto Bee in 1978, just five years before her death. Florence Thompson, it turned out, had always been angry about the famous image and considered it misleading, a violation of her privacy and a betrayal of a promise she claimed the photographer had made to her.
See an October 30, 1979 NBC News interview with Florence Thompson at Hulu: http://www.hulu.com/watch/71328/celebrating-mom-interview-with-florence-thompson-the-mona-lisa-of-the-dust-bowl