In Men at Lunch, director Seán Ó Cualáin tells the story of "Lunch atop a Skyscraper," the iconic photograph taken during the construction of 30 Rockefeller Plaza.
As shown in the film, people today still connected to the image, despite no one knowing who is in the photo and no one knowing who took the shot (it has been credited to Charles Clyde Ebbets since 2003). Many see their ancestors in it, though there is very little to corroborate this -- the men could be Irish, Scandinavian or anything else.
Ultimately, the film is interesting but never really gets to the heart of the matter and because of that drags a bit at times. While seeing the archives at Corbis is quite interesting, a few more answers might have been nice.