Earlier quoted context omitted.
In the US, railroads were granted sections of land (1 square mile) alongside tracks. I believe this was every other section, for each mile of track laid. One site I'm finding says that this extended 20 miles to either side of the track: Approximately 16 percent of Nebraska’s total land mass was given to various railroad companies, either by the federal government or by the state. Along the lines of the state’s two ma…
The standard land grant pattern for railroads was a checkerboard pattern, which makes it hard to depict accurately on a map. The source I have doesn't give an exact number of Nebraska that was actually granted in land grant to railroads, but 16% is right in the ballpark of what I'd estimate from interpolation from other states. However, it's also worth noting that land grants were only doled out in US history in an e…
I was aware of the "checkerboard" land-grant allocation, but not how deep (perpendicular distance from RoW) it went.
I also wasn't aware of how brief the land-grant subsidy era was. Though it would be interesting to see a track-mileage development timeline or animation showing how trackage developed over time.
My general understanding is that track mileage exploded quite quickly, often with competing railroads establishing duplicate connections especially on highly-attractive routes, with the winner then absorbing (or simply competing to death) the loser(s). There is also a distinction between major (national or regional) Class I railroads, and short-line (usually Class III) railroads, where a short-line often served only a single line or small set of lines within a small region.
Overall, US railroad trackage shrank for much of the 20th century as early, redundant, competitive trackage was abandoned. I'm not sure what recent trends have been.