Surveyors fixed the Four Corners point in 1875, and they put it where the law told them to. Chandler Robbins, working for the US General Land Office, ran the boundary between Arizona and New Mexico north from the Mexican border and set the monument where it met the 37th parallel. The National Geodetic Survey says the marker sits no more than about 1,800 feet from where it was meant to be.
The story that put it 2.5 miles out
A report in the Deseret News claimed that modern surveys had found the monument in the wrong place, as Nature’s news blog relayed it. A rebuttal from the National Geodetic Survey, dated May 15, 2009, said the figure that spread was 2.5 miles. Some reports also credited the discovery to the survey itself, which is part of NOAA.
The survey said it had made no such claim and had never suggested moving the marker. Its chief geodetic surveyor told Colorado’s Channel 9 news that the 2.5-mile figure was wrong. The Bureau of Land Management, the successor to Robbins’s employer, confirmed that the monument marks the point where the four states meet.
Why the line is not at 109 degrees
The mix-up goes back to the meridian. An 1863 Act of Congress, signed by President Lincoln, split Arizona from New Mexico along the 32nd meridian west of Washington, not of Greenwich. The Washington Meridian ran through the dome of the old Naval Observatory, at 77 degrees 03 minutes west of Greenwich. So the line Congress drew lay at about 109 degrees 03 minutes west.
The Geodetic Survey thinks the false error came from people assuming the target was exactly 109 degrees. Washington references were common. The boundaries of 11 western states use the Washington Meridian, and the US did not adopt Greenwich as its standard until 1912.
Robbins tackled the confusion at the time. In a letter to The Santa Fe New Mexican on November 1, 1875, he explained that the legal line lay a little under three miles further west than 109 degrees would have put it.
How he fixed the point
Robbins worked from the coordinates of Ship Rock, a landform in northwestern New Mexico. Those had been measured the year before by the US Geographical Surveys West of the 100th Meridian, led by First Lieutenant George Wheeler. At the northern end his line crossed the New Mexico and Colorado boundary, which an 1868 survey had run along the 37th parallel. Later surveys added the Utah boundaries and completed the cross.
So how far off is it?
The Geodetic Survey puts the gap between the monument and its intended spot at about 1,800 feet or less. That is roughly a tenth of the claimed error, and it runs the other way: the intended point lies west of the monument, not east. The survey adds that some uncertainty remains in fixing that offset exactly.
