This gentle approach had been learned in the 1930s when an agency called the Farm Security Administration was used photographic images to convince people that the miseries caused by the Great Depression — great as they were — could be first mitigated and finally overcome by the strengthening of the agricultural (and in due course industrial) economy. The result was what has to have been the most aesthetically potent propaganda campaigns of all time. I've written about this before. Click the FSA label in the panel at right to see these blog posts. The Prints and Photographs Division of the Library of Congress, which holds most of these photos, has collected some of them here.
When the US declared war on the Axis Powers the FSA photography unit was merged into the new Office of War Information and the emphasis of the group's documentary output shifted from Depression to war mobilization. I've shown quite a few OWI photos in previous posts. To see them, click the OWI label at right.
War mobilization meant that factories which had been making products for domestic consumption switched over to production of war materiel. The OWI photos show American workers making ships, planes, bombs, and all the other implements of war — large numbers of them being women doing jobs to free men for the armed services.
War mobilization also meant that the volume of traffic on the nation's transportation systems shot upward. And no traffic grew more than that of the railroads. As this graph shows, the numbers of miles of freight and passenger transportation by rail decreased substantially during the Depression years and then shot upwards to levels that have never since been equalled.
The war years of the 1940s were the glory years of US rail service and Jack Delano, one of OWI's documentary photographers, took pains to show its strength. Here are some photos from one shoot, made at the rail yards of the Chicago and North Western Transportation Company in December 1942.
In this one Delano shows both the great size of the yards and the volume of freight they handled.
In this detail notice the man on top of a freight car as well as the one at the rail switch.
Here you see a trainman walking toward the location where Delano is positioned. You can tell that Delano is standing on an overpass because of the dangling warning cords hung over the tracks above the man's head.
This photo shows an overpass such as the one on which Delano was standing to take the previous one. You can tell that the shoot carried over enough days so that some shots show snow on the ground and some do not.
I've stitched together details from two aerial photos of the Proviso Yards to show something of their scale. Click the image to view full size. The photos were taken a year or so before Delano did his shoot there.
Illinois Aerial Photos}
This detail shows where Delano was standing to take the second of the two images of the yard. I can't see a tower there but suppose there is one and that he's on it.
Delano's photos of the freight yards don't show many workers and it's apparent that this vast system required very few people to operate it. Here is the man who had main responsibility for the operation along with an assistant or maybe just a man on break.
Assistant or man on break.
Another detail from this photo.
And one final one.
Here are a couple of freight engines moving what is probably a long train of hopper cars.
Unlike the freight yards, the service areas show a fairly high concentration of men at work. Here are locomotives receiving some maintenance.
The captions of these photos explain their subjects.
Selected Bibliography and Related Web Sites about the FSA and OWI from the Library of Congress
Jack Delano, a brief biography from the Museum of Contemporary Photography
Oral history interview with Jack and Irene Delano, 1965 June 12 from the Smithsonian Institution
The Farm Security Administration page at the Library of Congress
Chicago and North Western Transportation Company on wikipedia
Chicago & North Western Historical Society
Links from the Chicago & North Western Historical Society
Chicago & North Western - A Capsule History
 My blog post on Fox Conner touches on this. The factory he ran switched from making "porous plasters" to alleviate back pain to making bullet-proof liners for the fuel tanks of airplanes and military tanks.
 See for example these photos by OWI's Ann Rosener taken in 1943 at a California shipyard.
 All the photos come from the Prints and Photos Div of the Library of Congress.