Meades Ranch Triangulation Station
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Geodetic Center of the U.S.
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Meades Ranch triangulation station, ca. 1940
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 Location of Meades Ranch in Kansas
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| Nearest city | Osborne, Kansas |
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| Coordinates | 39°13′27″N 98°32′32″W / 39.224087°N 98.542152°WCoordinates: 39°13′27″N 98°32′32″W / 39.224087°N 98.542152°W |
| Built | 1891 |
| NRHP Reference # | 73000772 |
| Added to NRHP | October 9, 1973 |
The Meades Ranch Triangulation Station is a survey marker in Osborne County in the state of Kansas in the Midwestern United States. The marker was initially placed in 1891; from 1901 to 1989, it was the reference location relative to which all locations in the United States were measured, and from 1913 to 1989, it was the reference location for all surveys in the continent.
In surveying, a geodetic datum is a point or set of points used to establish a coordinate system. By designating the location of one point, and the direction from that point to a second point, one can establish a system relative to which other points can be located and mapped. As one surveys a larger area over which the curvature of the Earth becomes significant, it also becomes necessary to define an ellipsoid: a curved surface that approximates the shape of the Earth in the area of interest.
The first nationwide datum in the United States was established in 1879. At that time, a region of contiguous triangulation existed from Maine to Georgia. The New England Datum was chosen with a benchmark in Maryland, near the middle of this region, as the horizontal datum, and a second Maryland mark used to define the azimuth (horizontal) direction. To account for the Earth's curvature, the datum used a model called the Clarke spheroid, developed in 1866.
The U.S. Coast and Geodetic Survey established a triangulation station, officially known as the Meades Ranch Triangulation Station, in 1891. The location lay near the intersection of two transcontinental arcs of triangulation: one running from the Atlantic to the Pacific Ocean, roughly following the 39th parallel; the other running from Mexico to Canada, along the 98th meridian.
In 1901, the Meades Ranch station was chosen as the United States standard horizontal datum: the point relative to which all land measurements in the nation were made. The choice was based on the station's location near the geographic center of the U.S. and near the intersection of the two arcs of triangulation, and because it minimized the number of changes in previously published positions. Its position was officially set as 39°13'26.686" N and 98°32'30.506" W; the azimuth direction to a triangulation station near Waldo, southwest of Meades Ranch, was officially set as 75°28'14.52" west of south.
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