Following on from my previous post Photographs That Changed the World I followed some links around on flickr, and finally ended up on the wikipedia article about Florence Thompson, the lady depicted in "Migrant Mother".  

In March 1936, after picking beets in the Imperial Valley, Thompson and her family were traveling on US Highway 101towards Watsonville in hopes of finding more work. On the road, the car timing chain snapped and they coasted to a stop just inside a pea-picker's camp on Nipomo Mesa. While Jim Hill and two of Thompson's sons took the radiator, which had also been damaged, to town for repair,[3][4] Thompson and some of the children set up a temporary camp. As Thompson waited, Dorothea Lange, working for the Resettlement Administration, drove up and started taking photos of Florence and her family.

She died at the age of 80, in 1983 and

her gravestone reads: "FLORENCE LEONA THOMPSON Migrant Mother – A Legend of the Strength of American Motherhood."

via wikipedia

Really interesting to read about the woman in the photography, and to read one of the citations which is about one of her daughters and the family's determination never to be in a similar situation again