is a derogatory reference to poor, migrant workers
during the Great Depression
. These people were unskilled, poorly educated workers, suitable only for menial tasks, such as harvesting crops, and, as such, received poor wages for working long hours under dreadful conditions. Many of these people were photographed by Dorothea Lange
The term "Pea picker" is used to distinguish a group as a lower social class from some other similar group, such as the "Pea-picking" Smiths, as opposed to the "Respectable" Smiths.
Temporary communities of Pea-pickers are called Pea Picker Camps and farms that employed them were Pea-picker farms.
Note the reference by character Lonesome Rhodes in Elia Kazan's A Face in the Crowd to pea-pickers as 'eating out of his hand'. They are understood to be equivalent to rednecks and hillbillies.