Arnold Reinhold writes "This month ends with the 125th anniversary of one of the most remarkable achievements in technology history. Over two days beginning Monday, May 31, 1886, the railroad network in the southern United States was converted from a five-foot gauge to one compatible with the slightly narrower gauge used in the US North, now know as standard gauge. The shift was meticulously planned and executed. It required one side of every track to be moved three inches closer to the other. All wheel sets had to be adjusted as well. Some minor track and rolling stock was sensibly deferred until later, but by Wednesday the South's 11,500 mile rail network was back in business and able to exchange rail cars with the North. Other countries are still struggling with incompatible rail gauges. Australia still has three. Most of Europe runs on standard gauge, but Russia uses essentially the same five foot gauge as the old South and Spain and Portugal use an even broader gauge. India has a multi-year Project Unigauge, aimed at converting its narrow gauge lines to the subcontinent's five foot six inch standard."