The international community recognizes a prime meridian that runs through the Royal Observatory at Greenwich in southeast London, England. It serves as a reference point for universal time and distance. However, that has not always been the case.
Latitude is easy. The equator divides the planet into northern and southern hemispheres quite logically. Longitude is arbitrary. Any spot can separate eastern and western hemispheres, and indeed, many spots have been selected for that honor and later discarded.
It’s not quite that simple if one expects the meridian to have any meaning. Any spot can be chosen but it has no purpose if people don’t recognize the resulting meridian and use it. This was particularly daunting in the nineteenth century when almanacs full of stellar calculations had to be published each year to support shipboard navigation. Only the wealthiest and most influential of nations could afford the luxury of maintaining a global meridian, countries like England and France, or nations seeking acknowledgment of their growing ascendancy like the United States.
The United States had no less than four meridians running through various points of significance within its capital city, Washington, DC: the Capitol Dome; the White House, the dome of the Old Naval Observatory and the clock room of the New Naval Observatory.
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The most significant of the four was probably the American Meridian which ran through the dome of the Old Naval Observatory, shown above. Its heyday stretched from about 1850 when it first emerged from Congressional legislation until about 1884 when an International Meridian Conference selected Greenwich as a universal standard. The American Meridian continued to exist until its eventual repeal in 1912 but by then had lost much of its practical usefulness. Thus the American Meridian served as a viable reference point only for about thirty-five years.
It wasn’t used for navigating the seas since Greenwich worked fine even for American sailors, however it provided genuine usefulness for another purpose — land surveying. The accuracy of nineteenth century surveying decreased as one moved further away from the common reference point. The United States was in the midst of carving out vast interior spaces into territories and states, and could not depend on a meridian on the other side of the Atlantic Ocean.
The American Meridian may not have lasted very long but it coincided with a vital cartographic period in United States history.
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Notice the prevalence of vertical lines of longitude drawn into several of the western states. Many of their borders follow whole integers of the American Meridian.
Failure to understand its existence sometimes leads to gaffes. There were widespread reports in April 2009 that the Four Corners marker had been placed in the "wrong" location. Actually it was located on the correct spot. The media, either not realizing or not bothering to examine the history of the American Meridian, had relied on the Greenwich Meridian by mistake.
While the American Meridian retains a legacy through the lines of longitude defining several of the United States, very little remains to commemorate the discarded prime meridian in Washington, DC today. The Old Naval Observatory now serves as the headquarters for the Navy’s Bureau of Medicine and Surgery. Public visitors cannot visit the observatory building, nor can they even access its grounds which are secured by armed guards and fences as part of protecting federal government facilities in the modern age.
Travel a few blocks due north however, and a tiny marker exists at the southeast corner of 24th & H Sts., NW, on the campus of George Washington University. The invisible line runs right through the university, cutting through some of its buildings such as New Hall and Ross Hall. The university recognizes its unique straddling of the old meridian and has included it in their "GW and Foggy Bottom Historical Encyclopedia."
It’s not Greenwich but it’s the closest thing on this side of the Atlantic.