I am planning to build a model railroad set in 1919.

My question is how do I figure out what cars existed in 1919, and in
what proportions?
The railroad itself is to be freelanced, running in northern Illinois,
near Chicago.

My goal is to create a railroad that is "plausible" or "believable".

One of my issues is not knowing what car details should or should not
exist. I understand that around that time new safety standards went
into effect, but I do not know what those standards are.

What books or reference materials would educate me?

Thanks
Phil Jannusch