I was searching around a bit to learn more about how real railroaders handle switchlists, and ran across Mark Mathu's page describing the analysis of a 1967 Green Bay and Western railroad switchlist. He and his friends not only shows the switchlist, but talks about the cars and industries being served that day.
It's interesting to see how the crews used abbreviations and shorthands for the industries they were probably serving daily. There's also no "from" field on the switchlist, nor is there any indication about what cars the crews would be picking up. I'm also surprised to see they noted the cargos on all the cars, perhaps as a double-check to make sure they had the right cars or knew where they would be dropped off.
I also like how they used every other line on the switchlist so they could write bigger; I should do that in my app.
It would be fun to do this kind of analysis for the SP in the 1930's. I might not be able to find a switchlist, but I might be able to guess from photos about the cars carried on a specific train.