US Standard Railroad Gauge or How MilSpecs Live Forever
The US standard railroad gauge (distance between the rails) is 4 ft 8 1/2in (1.44 m). That's an exceedingly odd number.
Why is that gauge used? Because that's the way they built them in England,and the US railroads were built by English ex patriots.
Why did the English build 'em like that? Because the first rail lines werebuilt by the same people who built the pre-railroad tramways, and that'sthe gauge they used.
Why did *they* use that gauge then? Because the people who built thetramways used the same jigs and tools as they used for building wagons,which used that wheel spacing.
OK! Why did the wagons use that wheel spacing? Well, if they tried to useany other spacing the wagons would break on some of the old, long distanceroads, because that's the spacing of the ruts.
So who built these old rutted roads? The first long distance roads inEurope were built by Imperial Rome for the benefit of their legions. Theroads have been used ever since.
And the ruts? The initial ruts, which everyone else had to match for fearof breaking their wagons, were first made by Roman war chariots. Since thechariots were made by or for Imperial Rome they were all alike in thematter of wheel spacing (ruts again).
Thus we have the answer to the original question.
The United States standard railroad gauge of 4 ft 8 1/2 in derives from theoriginal military specification (MilSpec) for an Imperial Roman army warchariot. MilSpecs (and bureaucracies) live forever!
Note: This has been proved to be an Urban Legend.