Ms. Lange came to Imperial County during the late 1930s, capturing a different generation of migrants drawn here from Mexico, the Philippines, Oklahoma and the Dakotas, looking for work in the carrot fields. In 1937, she photographed ramshackle tents lining a canal; a group of Model T’s making haphazard camp in a gully. In other shots, cabbage pickers bend deep and hoist baskets high on their shoulders.

Ms. Lange, best known for her Depression-era photographs of migrant laborers, began photographing bread lines and labor strikes near her San Francisco studio in 1932. In the 1920s, she had made her living as a society portraitist, photographing San Francisco’s wealthiest families — the Levi Strauss and the Haas families among them.

As the Great Depression worsened, she began photographing people she saw on the streets: men curled up sleeping or in line for food. In 1935, she married the economist Paul Taylor; they left San Francisco together to photograph the living conditions of agricultural laborers up and down the state, from Davis and Marysville all the way to Imperial County. The Farm Security Administration supported their work.