To drive to the actual geographic center of the nation, one needs to drive 13 miles on Hwy 85 north from the intersection of Hwy 85 and 212.
Turn left onto Harding County Road and drive 7.8 miles until you see a barn on your left hand side.
On the right side of the road you will see a orange metal posting standing about 50 yards into a pasture. At this location you will see the survey marker highlighting the "Center of the Nation".
How did we get this honor? This is what the U.S. Department of Commerce, Environmental Science Services Administration, Coast & Geodetic Survey tells us:
"Determining the geographic center of an irregular area on the earth's surface is a precarious business at best. There is no unique solution and none of any scientific significance. Several methods of approach are available. The one employed by the Coast and Geodetic Survey is probably best termed as the center-of-gravity method. Imagine a map of the area of which the geographic center is to be determined, has been placed on a piece of cardboard of uniform thickness and that his is cut carefully along the outline of the map. The center of gravity of this map outline, or what might be called the geographic center, is that point at which the map will balance.
The geographic center of the forty-eight conterminous states was determined by the Coast & Geodetic Survey in 1918 by the method described. This geographic center is approximately at latitude 39 degrees 50'N, longitude 98 degrees 35'W, near Lebanon, Kansas. When Alaska was admitted to the Union, the geographic center of the forty-nine states shifted about 439 miles northwest to a point at approximately latitude 44 degrees 59'N, longitude 103 degrees 38'W, about eleven miles west of Castle Rock, Butte County, South Dakota. In arriving at this determination the geographic center of Alaska was determined by the method described and was found to be at latitude 63 degrees 50'N, longitude 152 degrees 00'W, with an uncertainty of about 15 or 20 miles in any direction. The geographic center of the combination of Alaska and the forty-eight conterminous states is considered to be on the great circle connecting their geographic centers at a point where the two areas would "balance"; i.e., considering each having a weight, proportional to its area, concentrated at the corresponding geographic center.
Later when Hawaii was admitted to the Union, its geographic center was determined to be at latitude 20 degrees 15'N, longitude 156 degrees 20'W, with an uncertainty set at about 3 or 4 miles in any direction. The geographic center of the fifty states was then determined as being on the great circle connecting the geographic centers of the forty-nine states and Hawaii at a point where these areas would "balance." The effect of including Hawaii was rather small since its area is only about 1/560 of that of the forty-nine states. The geographic center of the fifty states, thus determined, then shifted about six miles west-southwest to latitude 44 degrees 58'N, longitude 103 degrees 46'W, which is approximately 17 miles west of Castle Rock, Butte County, South Dakota. The uncertainty of this determination is set at about 10 miles in any direction.
Below is the Data Sheet on the Center of the Nation Survey from the National Geodetic Survey Website.
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