This is a list of geographic centers of each U.S. state. Note that the geographic center of the entire U.S. is northeast of Belle Fourche in Butte County, South Dakota 44°58′N 103°46′W, while that of the contiguous 48 is near Lebanon in Smith County, Kansas 39°50′N 98°35′W. The geographic center of North America lies near Rugby, North Dakota 48°22′2″N 99°59′46″W, though this designation has no official status.
Updated list of geographic centers
The list above has been only slightly modified since it was first produced by the U.S. Geological Survey (USGS) in the early 1920s. At that time, the center for a state was found by suspending a cardboard cutout of the state by a string, and then drawing a vertical line from the suspension point. After rotating the cutout 90 degrees and drawing another vertical line from the new suspension point, the intersection of the two vertical lines was used as the geographic center. The result is dependent upon the type of projection used. Although there have been different definitions offered for the geographic center, an intuitive one, and one used by the USGS, is "the center of gravity of the surface, or that point on which the surface of the area would balance if it were a plane of uniform thickness." An updated list of geographic centers using this definition (which is equivalent to the state's centroid) is given below. It was derived by minimizing the sum of squared great circle distances from all points of land in a state (including islands, but not coastal waters, following the earlier practice of the USGS). It represents a slight improvement over the list originally published
The geographic center of the contiguous United States, determined in this way, is at (39.8000 N, 99.1086 W); this is 2.7 miles from Agra, Kansas, 4.7 miles from Kensington, Kansas, and 27.9 great circle miles west of the longstanding designated center of Lebanon, Kansas.