Before then, most towns set their clocks by the sun, and railroads ran on some 50 different times, causing confusion and accidents. The railroads adopted a plan developed by William F. Allen of the General Time Convention. At noon on the 75th meridian, telegraph signals from the Allegheny Observatory in Pittsburgh let stations reset their clocks. Many cities followed the railroads' lead. Congress did not make standard time law until 1918.
In the 19th century, noon arrived at slightly different moments in each town, depending on its longitude. When it was noon in Chicago, it was 12:31 in Pittsburgh and 12:24 in Cleveland. Each railroad kept its own time, usually that of its headquarters, and large stations had several clocks showing the times used by different lines.
The Canadian engineer Sandford Fleming promoted worldwide time zones, and in the United States the scientists Charles Dowd and Cleveland Abbe had proposed standard zones. The railroads acted on their own. In October 1883, the General Time Convention adopted Allen's plan dividing North America into Intercolonial, Eastern, Central, Mountain and Pacific time, each based on meridians 15 degrees apart. On Sunday, November 18, 1883, jewellers and railway officials waited by their clocks. In the eastern part of each zone, clocks were set back, so noon struck twice.
Some resisted. A few cities kept local time for years, and preachers objected to changing God's time. The International Meridian Conference in Washington in 1884 chose Greenwich as the prime meridian. The Standard Time Act of 1918 finally put the zones into federal law.
Key people: William F. Allen, Sandford Fleming