The Four Corners Monument Is In The Right Place

So there!:

Recent media reports incorrectly stated that the location of the Four Corners survey monument – marking the point common to Arizona, Colorado, New Mexico, and Utah – is in error by 2.5 miles and suggested that the monument therefore does not correctly mark the intersection of the four states. These reports also erroneously attributed the discovery of this supposed error to the National Oceanic and Atmospheric Administration’s (NOAA) National Geodetic Survey (NGS). ... NGS has, however, worked with the media to correct inaccuracies in the initial reports, clarifying that the distance between the actual location of the monument and its intended location is substantially less than the reported 2.5 miles, and that – as affirmed by the Bureau of Land Management (BLM) – it does indeed correctly mark the four-state-intersection point. ...

In 1875, a surveyor named Chandler Robbins was contracted by the U.S. General Land Office (GLO), the BLM’s predecessor, to survey the entire boundary between the territories of Arizona and New Mexico, from the U.S.-Mexico boundary to the 37th parallel of latitude north of the equator. He was charged with also establishing, at the boundary’s northern terminus, the Four Corners monument, as it would be known upon completion of the other territorial boundary surveys terminating there. Robbins was directed to base his survey on the geographic coordinates of Ship Rock (a prominent northwestern New Mexico landform), which had been determined the previous year during the decade-long U. S. Geographical Surveys West of the 100th Meridian, led by First Lieutenant George Wheeler.

An 1863 Act of Congress, signed by President Lincoln, which separated Arizona from New Mexico, specified that the dividing boundary should be coincident with the 32nd meridian of longitude west of the Washington (DC) Meridian. The Washington Meridian, which had been in use since 1850, was defined as bisecting the dome of the old Naval Observatory, situated at a longitude of 77 degrees 03 minutes West (for simplicity, longitude values presented here are rounded to the nearest arc minute). In fact, the boundaries of 11 western states are similarly longitude-referenced to the Washington Meridian, and not the Greenwich Meridian. This practice was in place in the U.S. until 1912, when our nation adopted Greenwich as its standard longitude reference.

Hence, what Congress had specified for the Arizona-New Mexico boundary, and the Four Corners monument, was that they should be established at a longitude of 109 degrees 03 minutes West, as referenced to the Greenwich Meridian. Therein, we believe, lies the source of the invalid report of a Four Corners monument location error of 2.5 miles. Some people apparently relied on the incorrect premise that the marker was originally intended to be located at a longitude of exactly 109 degrees West. But, Robbins followed his marching orders correctly, and the Four Corners monument was established at the point he determined, to the very best of his ability and using the available technology, to be the prescribed location of 109 degrees 03 minutes West longitude and 37 degrees North latitude. There, his meridian survey intersected the 1868 New Mexico-Colorado boundary survey, which ran along the 37th parallel. Subsequent surveys established the Utah-Colorado and Arizona-Utah boundaries, thereby completing the Four Corners assemblage of territorial (eventually state) lines, as specified by Congress.