Even a casual user of a map of the State of New Mexico will notice the coincidence of its exterior boundaries with lines representing degrees of latitude and of longitude. Looking at the Arizona line however, the layman and perhaps some surveyors will ask themselves if early surveyors made a blunder in their determination of longitude and missed the 109th meridian as badly as John Clark in 1859 had missed the 103rd. This time the answer is no, for the west boundary of New Mexico was run on the 32nd meridian west of Washington DC.
The boundary was created in 1863 when New Mexico Territory was divided and its western portion became Arizona Territory, however the line was not surveyed until 1875.
In examining maps of past centuries, some knowledge of the history of prime meridians will come in handy. Until little over a hundred years ago most countries used more or less their own meridians, the selection of which was based more on patriotism and whim than on geographic considerations. In Europe alone, more than a dozen different prime meridians were in general use at one time or another. The Greenwich meridian was widely used at sea only because of the prevalence of the British Admiralty charts.
The United States was not to be outdone. In 1804 a line was run through the center of the White House and designated as zero point for the Washington meridian. This did not prove to be a good choice. The British had made a similar emotional decision when they adopted the London meridian based on the cross on St. Paul’s Cathedral. More practical men soon realized that the best point of origin for a country’s maps is at an astronomical observatory.
An Act of Congress of September 28, 1850 (9 Stat. 515) provided for the adoption of the Washington meridian. The Act stated that “hereafter the meridian of the observatory of Washington shall be adopted and used for all astronomical purposes . . .” The Washington Meridian passes through the dome of the old Naval Observatory, located at 24th Street and Constitution Avenue in Washington D.C. Its longitude is 5 hours, 8 minutes and 12.15 seconds (of time) west of Greenwich, which equals longitude 77°03’02.3”
The Washington meridian was not legal for nautical purposes, there the Greenwich meridian stood alone. During the six decades the act was in force, the meridian of Washington described the boundaries of eleven Western states, Kansas being the first in 1861 and Arizona the last.
In the end, it was the United States more than anybody else that recognized the need for an universally accepted point of reference. As a result of a presidential invitation twenty-five countries sent representatives to the first International Meridian Conference which opened on October 22, 1884 in Washington D.C. There, a resolution was passed that stated among other things: That the Conference proposes to the governments here represented the adoption of the meridian that passes through the center of the transit instrument at the observatory of Greenwich as the initial meridian for longitude.
After that the Washington meridian became an anachronism and the act that established it was repealed August 22, 1912 (37 Stat. 342)