Why did the railroads initially divide the United States into four standard time zones?
Standardized time is important to prevent collisions on railway lines. Many countries use different solutions. Russia uses Moscow time as a railway standard.
Before railways, each town or city created their own time by using solar noon, where they were, to set their clocks to. Nothing moved fast enough to really cause much of a bother.
Trains often ran on a single track which had to be shared. This made timing a crucial element because each train starting many miles apart and possibly without direct communication (telegraph only, no radios) had to avoid one another with minutes to spare.
Each railway company in the US and Canada used its own standardized time initially. The four time zones for railways were agreed upon in 1883 but places held out into the 1900s. Federal law in the US standardized time zones for all in 1918.
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