Many of the supplies that kept the US Army going in Europe were taken from the American heartland by rail to ports of embarkation. New York City was a major port then as it is now.
A single Liberty Ship could hold as many as 300 box cars full of supplies. Naturally, I determined that means I need to have 300 box cars in my collection. I don't have that many yet, but I am working on it. Recently I posted some photos of a few of my refrigerated box cars, here are some for dry goods.