1884: Geographers and astronomers adopt Greenwich as the Prime Meridian, the international standard for zero degrees longitude.
The late 19th century was an era of standardization. With the Second Industrial Revolution stimulating world trade, the Treaty of the Meter established the International System of weights and measures in 1875. With railroads linking together entire continents, nations were replacing hundreds (or even thousands) of diverging local times with a system of hour-wide time zones. (The United States adopted its zones in 1883.)
Amid all this, navigation at sea -- and the charting of stars in the heavens --
often remained a matter of local, national or even religious preference. Maps might be based on longitude east or west of Jerusalem, Saint Petersburg, Rome, Pisa, Copenhagen (think Tycho Brahe), Oslo, Paris, Greenwich (just east of central London), El Hierro (in the Canary Islands), Philadelphia (former U.S. capital) and Washington, D.C. These divergent reference meridians -- representing a mixture of astronomical, theological and maritime power -- ranged over 112 degrees of longitude.
You could do the math, but that meant you did the math. These were the days before computers and even the bulkiest of mechanical calculators. Got abacus?
Many state boundaries in the U.S. West were determined by the Washington Meridian, which then ran through the Old Naval Observatory in the Foggy Bottom neighborhood. But an 1850 law established its use...
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