I found this while looking for some other items of interest:
https://archive.org/details/seaboardairliner1914seab
On the left of the screen you'll see a box that says "View the book"
Right click on "PDF" and "Save Link As" to save it to your computer, it's large (almost 600 pages) but there's a load of useful info in it if you're interested in what kind of commodities Seaboard (and other RRs) would have carried.
So take a look and give your rolling stock a purpose of being 
