For a singular image of the Great Depression and the roughness of those years, it's hard to do much better than Dorothea Lange's 1936 photograph of Florence Owens Thompson, two of her children tucking their faces over her shoulders, a baby in her lap.
Where that image comes from, there are many, many more: around 175,000 surviving portraits of America between 1935 and 1945 taken by the photographers of the government's Farm Security Administration. The Library of Congress, which houses the collection, has, remarkably, digitized all the negatives and tagged the records with loads of data, such as who took the picture and where it was taken.
Now, thanks to a new project known as Photogrammar from Yale University, viewers will have a much easier time exploring the photographs. There's a map that displays the images by county and another that shows where each picture was taken and by which photographer. There's also an interactive that allows viewers to sort the photos by theme (e.g. "war" or "religion") and then browse from there. Other tools are still in the works.
Whether by geography or by theme, it's worth spending some time playing around in this vast archive to build a greater visual sense for that period in American history. Here are a few of my personal favorites so far: