From the Great Depression to Japanese-American internment, Dorothea Lange's camera bore witness to some of the darkest moments in US history

A large sign reading "I am an American" hangs in the window of a shuttered Oakland grocery store the day after Pearl Harbor, as a 1940s car sits in the foreground.

In 1936, Dorothea Lange approached Florence Owens Thompson – a 32-year-old sheltering with her children at a California pea-pickers' camp – and took one of the most recognizable photographs in history.

Migrant Mother portrays her with two children pressed against her shoulders, staring into the middle distance with an expression that seems to contain the entire weight of the Great Depression.