You can find some more information about this photo in the following
interview (look for "Lange" once you get there).

http://www.photowings.org/pages/index.php?pgA73

Basically, John Szarkowski found out that the words "end of an era" was more of a personal observation by Lange for the widow in the photo (her husband is dead and it's the end of her life as she knew it) , and not a social observation. Then Szarkowski makes the comment about how malleable photos are, and how the makers frequently try to nail down the possible interpretations with titles, text etc.

-Bill