I'd like to learn some real basic stuff about how rail companies own, operate and/or share track. I assume this has a lot to do with mergers & acquisitions, government regulation and era. But for example, I'd like to know at least enough so I can at least ask intelligent questions. As it is, I don't even know if "Did Southern Pacific and Union Pacific service the same cities?" is a stupid question or not. I know it's an uninformed one. So I guess what I need is a "How Railroads Work" book, but one that deals more with the use and building of infrastructure, and less with the specifics of the technology. I already suspect I'm using terminology incorrectly, so a detailed glossary would be great, too, if you'd like to recommend one. I'd like something closer to an encyclopedia rather that a glossary with one-liners for things. As always, thanks so much for your patience, folks.