One more item from downtown Chicago, at least until the next time I go there. This plaque, near the junction of LaSalle and Jackson for over 40 years now, memorializes something few people give much thought — few people give it the time of day, you might say. Time zones.THE STANDARD TIME SYSTEM IN THE UNITED STATES ADOPTED ON THIS SITE — OCTOBER 11, 1883.

Chicago’s famous Grand Pacific Hotel, then on the site of the present Continental Bank building, was the location of the General Time Convention of 1883 which, on October 11 of that year, adopted the current Standard Time System in the United States.

The Convention was called by the nation’s railroads. Delegates were asked to develop a better and more uniform time system to govern railroad operations.

Previously, time had been determined by the position of the sun, with high noon as the only existing standard of exact local time. More than 100 different local times resulted from this method.

The new plan, proposed by William F. Allen, Convention Secretary, established four equal times zones across the country, each one hour ahead of the zone to its west. All railroad clocks in each zone were to be synchronized to strike the hour simultaneously.

The Standard Time System was inaugurated on November 18, 1883. On that Sunday, known as the “Day of Two Noons,” the Allegheny Observatory at the University of Pittsburgh transmitted a telegraph signal when it was exactly noon on the 90th meridian. Railroad clocks throughout the United States were then reset on the hour according to the time zone.

Although implemented by the railroad, the Federal Government, states, and cities began to use the system almost immediately. On March 19, 1918, Congress formally acknowledged the plan by passing the Standard Time Act.