Thanks and welcome aboard. I will include your tag in my future post. Just a quick note on how I see it rolling out. We have the United States Railroad page as an anchor and jumping off point to the states. Each state can have their own space page on the rail roads that operated in the state. Most companies span across multiple states, but their interactions and effect on each state, community, etc. will be different. So even though we are writing multiple space pages on the same company, they are unique. A page can be written for each county within the state, where you can explore more in depth, the depots, railroad jobs and short lines.
The category pages were already started. I don't know if we have to live with what is there, but I see some putting subcategories for companies that later merged, and for the same railroad company, but for a particular county. I would rather it be the United States with each railroad company below that. The only reason for a subcategory to the railroad company is if it were a subsidiary.
Each railroad company should have one page to describe the company's history. This is the history of the company, not small town America (which is explained in the state pages), so we should only have one page per company, even though they span multiple states.
I can see later people wanting to do commuter, inter-city and short lines, but these should probably have their own sub-level, not just grouped under the United States page. I don't think you can group these by state or county, because even though some would only service one state or county, others will cross state or county lines.
Anyway, this is my game plan. I don't know if that meets your needs. I'm open to suggestions.