Today the whole world counts lines of longitude away from Greenwich, England. But the globally accepted prime meridian running through the Royal Greenwich Observatory is a relatively new development. At one time, most every important city had its own line: Rome, Jerusalem and St. Petersburg, among others. Of course, for a meridian line to be taken seriously by navigators and mapmakers, one had to publish an ephemeris, viz. an almanac of points on the ground and their relation to points across the Milky Way. Like with all competing standards, a shakeout eventually occurred, and by the time American democracy started teething, most everyone oriented themselves from either Greenwich or Paris.

In the New World, things were different. For one, there was the impracticality of using meridian lines based across the pond: because the Atlantic's width was occasionally reassessed, so too would the ephemerides have to be updated. Following this standard would subject American locations to constant revision -- even though they hadn't actually gone anywhere.

A strong secondary consideration was the symbolic value of having a prime meridian to call our own, just for the sake of national identity. Thomas Jefferson in particular would be damned if he'd let the U.S. measure from England. So in 1804 -- just after the Louisiana Purchase and right as Meriwether Lewis and William Clark were heading out -- he had the first American meridian drawn up. Jefferson's meridian bisected his living quarters at the time (the White House) and ran the length of 16th Street NW from geographic pole to geographic pole. Meridian Hill (Malcolm X) Park, which lies along 16th Street between Columbia Heights and Adams Morgan, draws its (non-militant) name from this historical factoid.

But 16th Street never quite took off, and in 1849 Congress authorized a Naval appropriations bill moving the line six blocks over to dimidiate the Naval Observatory's central dome at 24th Street NW, on a small outcropping in Foggy Bottom. And decorated Naval officer Charles Henry Davis was charged with creating the first annual almanac: the American Ephemeris and Nautical Almanac.

Davis made sure the necessary star tables were drawn up for nautical use, but the American meridian was too late to catch on with the boat people; by this time, two-thirds of the world's commercial ships followed Greenwich. The landlubbers, on the other hand, found it quite useful. With westward migration really taking off around mid-century, and with Horace Greeley (or John B.L. Soule at any rate) imploring young men to go west and grow up with the country, these were halcyon days for the American Meridian.

Not until after the confusion of the Civil War did it really get a proper workout -- but in subsequent years the line was used to establish boundaries of most western states, including Colorado (eastern border = 27 degrees west of 24th Street), Arizona (32 degrees), and the Oregon (42 degrees). Then in 1850, at Davis' encouragement, Congress split the difference and passed legislation declaring: "The meridian of the Observatory at Washington shall be adopted and used as the American meridian for all astronomical purposes, and the meridian of Greenwich shall be adopted for all nautical purposes."

But that didn't last for long, either. In 1884 President Chester A. Arthur brought delegates from the world's powers together to settle on a single prime meridian. It should come as little surprise that Greenwich won out, and the system as we know it today was fixed. In 1912 Congress finally got around to officially abolishing the American Meridian.

So what's left of the old system? The old Observatory, now a historic site, remains. In 2000, George Washington University embedded in the sidewalk a strip of granite with the words "AMERICAN MERIDIAN," and mounted an explanation above it, on campus at 24th and H Street NW. But there's something funny about the plaque. For one, it lists 1848 as the date of the meridian's designation, but doesn't explain. It also breathlessly declares:

To your left is the hemisphere of the Atlantic, the hemisphere of Europe and Africa, of Roman numerals and Indian script, of the Silk road and the rising sun.

To your right is the hemisphere of the Pacific and the American West, the hemisphere of Japan and China, of calligraphy and rocketry, of towering volcanoes and the starry night.

Beneath your feet is the line that divides the two."

Once you get past the purple prose, it almost seems to be saying that in the old American system, Japan and China were in both the East and West hemispheres. Hmmm. Maybe Greenwich isn't so bad after all.

To visit the American Meridian marker, take the Orange or Blue lines to the Foggy Bottom station. Exit to 23rd Street, turn right and walk down to H. The plaque and line are one block to the right, on the south side of the street.