. >> dorothy lang -- the woman's som. >> dorothy lang caught the picture. is a unique copy of the picture as it was originally taken. >> migrant mother is a part of a new deal project to capture poverty in rural america between 1935 and 44 -- and 1944. >> in 1944, we are in the midst of the war, the depression is recently passed, and the attitude is, who will ever want to look at these sad old pictures again? the librarian of congress went over and said, i know it is a lot of photographs, more than 170,000, but i feel that if we collect today, contemporary, in 50 years, and did 100 years, that will be a visual encyclopedia of life in the united states, the good as well as the bad. >> today, this is the library's most popular photo collection. it is also possible to track the country's history in the map division. >> this is the ground fuel of any collection. it is the first document on which the name america appears. because the person who made them that -- made the map made -- named america in honor of the merval vespucci. we can tell you how did america c