May 1943. "Nearly exhausted sulfur vat from which railroad cars are loaded. Freeport Sulphur Company at Hoskins Mound, Texas." View full size. 4x5 Kodachrome transparency by John Vachon, Office of War Information.
"Interesting. A crane on the rails. Was it attached to a rail car of some sort?"
If you look at the full size version of the picture you can see that the crane is part of a rail car. It is turned sideways to handle the sulfur which is why the back end sticks out over the sides of the rail car.
Crane cars are hardly uncommon. Most railroads have a wreck train on call at division points in the event of serious derailments and those trains invariably include a crane. For an industry like this where they are using trains to move product out of the pit a steam crane mounted on a railroad car is just about ideal - mobile and doesn't require extra space to move in. These days of course most open pit mines don't use rails to move product out but truck that would make your basic monster truck look like a Hot Wheel.
