Liberty Industrial Spur

[FCIN]

By "fluff" I was talking about things such as a history for my railroad, and it's purpose (...)

As far as a history for your railroad, you could go with any number of prototype scenario's where the line represents a short segment of a now abandoned main line that was preserved in order to continue service to the large industry (whatever you decide it should be). You can find a lot of contemporary short line or main line operations where this is the case if you spend a little time looking around. Over the past 30 years or so, many a short or even long branch line has become an independent short line because the big roads no longer wanted to deal with them and the short line could offer better service.

A typical example could be that when lines ABC and XYZ merged, line XYZ became redundant and was abandoned except in a few locations where active industries were located. Line ABC operated these branches at first, but quickly sold them off to short line or industrial switching operations and thus your railroad came in to being.

I can't seem to settle on a topographic location so I guess that should be my first step.

A small switching operation like what you're proposing could be located just about any where you choose. I'd maybe just keep in mind the type of terrain you want to model, but even that is not a big issue as an industrial area like what you're modeling would, for the most part, be quite flat. Maybe some low hills, lots of trees and bushes, and one or two non rail served structures, in areas that are strictly for scenery.

Since your primary motive power (right now) is an SP prototype, then just pick a location that used to be SP and that appeals to you and go with it. Keep in mind that your upstart railroad probably purchased the locomotive used from either the SP or a locomotive dealer (or was included in the purchase of the branch) and it hasn't been painted yet (got to earn a little revenue first) or you could just paint out the SP lettering and substitute your own road name and reporting marks.     You could even say that your railroad painted and lettered the locomotive in SP colors to show the lines heritage. Several actual short lines have done just that.