Earl writes:
> the fact that the CO/NM state line shifts about a 1/2 mile southward just east of Edith, CO. According to my DeLorme Atlas
Earl and others,
That's nothing. The southwest corner of CO should be 37N 109W exactly per definition. That also defines the "four corners." Go look at the four corners monument on GoogleEarth and look at the lat/long. Then scroll over to exactly 37N 109W. You'll have to scroll east about two miles! The four corners monument is about TWO MILES inside of Arizona. The gross error is something that comes up here in New Mexico now and again. That corner was established long before radio time stations and GPS. In those days, position was based on celestial observations and the sun with longitude the most difficult as it depends on very accurate time. In those days, accurate time was the chronometers the surveyors and railroad maintained. A few seconds of time error could displace the longitude a half-mile or more. Those early surveyors did the best they could for the time. If you want to see a real surveyors mess, look at New Mexico's southern border! All due to swapping land back and forth to settle legal disputes and trying to correct the original surveying errors.
Though back to the OP, I too wonder what legal or practical purposes the state signs along the rails served. I photographed several of them on a recent trip from the Antonito end and wondered the same.