Here are some photos (and artworks) of the grain elevators of Chicago, c. 1860s.
I found it very difficult to visualize the scene and how "grand" this whole system was. These pictures somewhat grasped the immensity of the system.
(this photograph is a nice layout of what the elevators are actually like)
(this photograph is composed mostly of lumbers and I believe there are grain elevators in the background)
(an artist named B. J. O. Nordfeldt etched some interesting images of Chicago from the mid-1920s [so, they are more recent than the other photographs]. His style and composition is really quite different from all the paintings we have seen, but he provides an interesting new view of what Chicago was like back then)
More of Nordfeldt's etches can be found here: