Not just you who mentioned it, but some context here is good. Probably 95% of the track (or more) in the Confederacy was either 4'8'' or 5' gauge. That 5 percent? A few miles of track had been laid in 5'6'' west of the Mississippi. Since there were no crossings of the Lower Mississippi in those days, a different gauge on the other side of the Mississippi wouldn't have mattered until a couple of decades after the end of the war. And Virginia and North Carolina were the only states that rocked the 4'8''. Most everywhere else was 5'. I feel like this is one of those factoids that gets repeated over and over, but it's not like you had to switch trains every twenty miles or something because there 5 different wacky gauges. As long as a person wasn't going to NC or Virginia, it wouldn't be an issue.
You are absolutely correct here. I did some of my own research after you first posted this and the issue comes from the proliferation of 3' and 3'-6" Narrow Gauges in the south in the 1870s-1890s, particularly as railroads were built into more mountainous areas where a narrow gauge greatly reduced construction costs (much easier to build on a mountainside or dig a tunnel if your gauge is narrower). And living in Virginia, yes, I'm used to seeing different historical gauges all over the place, and this affected my perceptions. I used to work for Norfolk Southern (back in the late '90s/early 2000's when they actually believed in Safety First, mind you), which ultimately absorbed many non-standard gauge RRs across the south, mostly, looking back, built after the war, and I let my memories of all these narrow gauge post-war lines affect my judgement.
For additional clarity, it wasn't
just Virginia & NC that had 4'-8", though primarily the case. There were a few 4'-8" areas elsewhere, such as a "Y" near Montgomery. The below map is from Wikipedia, and I can't absolutely attest to it's complete accuracy, but it does show that 4'-8" and 5' ruled VA-NC as you stated, but other places did see non-5' gauge outside of these two States. As railroads expand into the mountains Post War iTTL, a narrow gauge will most likely (almost certainly) be chosen for practical engineering reasons.
Whether there's ever a push to standardize, or any money to support this, will depend a lot of Post War politics and whether the Jeffersonian Dems and States Rights folks (e.g. Gov. Brown and his political offspring) will be willing to support something as Whiggish as a unified national gauge, let alone be willing to spend the multiple millions to make it happen. My gut feeling is still that 2-4 gauges will proliferate through the 19th and early 20th centuries at a minimum.
And of course, all railroads were built by private companies in those days.
Some clarification is needed here. When I said "built by private companies" I didn't just mean the RR company itself, but the
investors, e.g. they were Privately Funded and Constructed. The V&T, ETN&V, and IIRC G&T, by contrast, were built in part from State funds (what we today would call a "public-private partnership" or PPP). In the case of the V&T, it was a very controversial move and was nearly defeated in the VA House of Delegates (Floyd had an ally fake fainting to buy time!) because of Democratic opposition to public infrastructure spending on ideological principles (VA Dems of the time were very much Jeffersonian in their suspicions of any government investments). The V&T's biggest proponent, future Governor John B. Floyd, was a Democrat too, but SWVA Dems at the time were somewhat "Whiggish" when it cam e to infrastructure expansion, as they knew it was necessary to make their region into more than a backwater.
The V&T was (per Noe) also specifically built with the political intent of connecting Richmond to the West and Deep South with the intent of increasing ties in the advent of secession (making Virginia overtly "Southern"). William "Extra Billy" Smith and Henry Wise in particular were hoping to both tie Western VA closer to Richmond and Richmond closer to the South (prior to 1851 there was open talk of the western VA counties breaking away to form a new State; e.g. William Burwell).
The greater point here is the
motivation behind the railways. Most of the wholly private ventures were intended for strictly commercial purposes, and usually to benefit the investors, primarily plantation owners. No one cared about any greater plan for connecting Atlanta to Richmond, for example, just getting Thaddeus Farquhar's cotton to Charleston harbor. Thus most ran straight to a port with no intention of connecting into a larger network, there to take cotton and other crops to ships, not facilitate interstate transit. Other lines later branched off of those original trunks over time to fulfil similar commercial means, and eventually interconnected in an organic, ad hoc manner. Eventually interstate travel from Atlanta to Richmond through the Carolinas by rail was possible, but through a maze-like network of mostly interior-to-port lines with numerous train changes along the way.
The VA-TN-GA corridor was different in that it had Public investment with a specific political/strategic purpose: Interstate connectivity to unite the future Confederacy that some Fire Eaters were already discussing in 1848. This line not only benefited the Great Valley economically, it allowed direct travel from Atlanta to Richmond in a straight shot, possibly without changing trains. The RR brought local goods to ports, but it also solidified economic ties between the region and Richmond and the Deep South (as was an overt part of the political motivation), such that by 1861 SWVA greatly favored secession compared to the more isolated NWVA, even though in 1851 prior to the new VA constitution the two regions were of a like mind when it came to "those highfalutin planters out east".
The effects of these two different approaches can be seen in the war. Prior to 1863 the CSA was able to quickly dispatch armies between theaters following the direct V-T-G line. After Knoxville fell to the Union in '63 Bragg had to send forces via this maze of RRs, with numerous train swaps. The coordination between these routes was largely non-existent, and private freight was often (frustratingly for the CS Army) given priority over the war effort. They even suffered a couple of head-on collisions between trains. As such, it took 3-4 weeks to accomplish what had previously taken days.
