On 18 November 1883, U.S. and Canadian railroads usurped local time, implementing four continental time zones to manage passenger and freight trains. They called it Standard Railway Time (SRT).
Rather than turning to the federal governments of the United States and Canada to create a North American system of time zones, the powerful railroad companies took it upon themselves to create a new time code system. The companies agreed to divide the continent into four time zones; the dividing lines adopted were very close to the ones we still use today.
The U.S. government did not get involved in timekeeping until 1918, when it introduced daylight saving time.
Before clocks, people marked time by the sun and the phases of the moon. With the development of the railway and the invention of the telegraph, accurate time became more important. Prior to adopting SRT, trains traveling east or west between towns had a difficult time maintaining coherent schedules and smooth operations. The new time zones were each one-hour wide, simplifying train schedules and virtually everything else in increasingly industrialized America.
Impetus for the adoption of standardized time, however, did not originate with the railroads. Astronomers and geophysicists, trying to get simultaneous observations from scattered geographical locations, had long advocated standardized time.
America’s industrialization trailed that of Europe. For example, England, Scotland and Wales had developed a railway standard time in the 1840s.
The Royal Observatory in Greenwich began transmitting time telegraphically in 1852 and by 1855 most of Britain used Greenwich time.
It’s not as though Americans cared nothing about time. But clocks were not synchronized across localities. Humans seem to have marked the passage of time as far back as we have found records.
Ice-age hunters in Europe over 20,000 years ago scratched lines and gouged holes in sticks and bones, possibly counting the days between phases of the moon. Five thousand years ago, Sumerians in the Tigris-Euphrates valley in today’s Iraq had a calendar that divided the year into 30 day months, divided the day into 12 periods (each corresponding to 2 of our hours), and divided these periods into 30 parts (each like 4 of our minutes). We have no written records of Stonehenge, built over 4000 years ago in England, but its alignments show its purposes apparently included the determination of seasonal or celestial events, such as lunar eclipses, solstices and so on.