Geographic Center of the United States: Kansas, South Dakota or Missouri?

The geographic center of the contiguous 48 states is near Lebanon, Kansas, at about 39°50′ N, 98°35′ W. The geographic center of all 50 states is in Butte County, South Dakota, about 20 miles north of Belle Fourche, at about 44°58′ N, 103°46′ W. A third "center" is the Census Bureau's center of population, which in 2020 was in Wright County, Missouri.

The two geographic centers are about 443 miles apart, in two counties you can browse on the Kansas county list (Smith County) and the South Dakota county list (Butte County); the distance is our geodesic calculation between the published coordinates. Adding Alaska pulls the center far to the northwest, and Hawaii pulls it back only slightly, because Alaska has almost 90 times the land area of Hawaii.

The Lebanon, Kansas figure is usually traced to a 1918 estimate of the center of the 48 states by the U.S. Coast and Geodetic Survey. The method usually described is a physical one: cut the outline of the country from a sheet of uniform material and find the point where it balances. That is the same idea as the definition the USGS still gives, the point on which the area "would balance if it were a plane of uniform thickness".

The shape of the lower 48 has not changed since Arizona and New Mexico became states in 1912, so the estimate has never needed revising. What has changed is how much weight people put on it. The USGS states that no government agency has established a marked or monumented geographic center for the conterminous states, the 50 states, or North America. The monument near Lebanon was put up by a group of local citizens, who hired engineers to determine the position.

The USGS also notes that Meades Ranch triangulation station, about 12 miles north of Lucas, Kansas, is often confused with the geographic center. Meades Ranch was the origin point of the national triangulation network, the reference for property and boundary surveys across North America for much of the 20th century. It is a geodetic landmark, but not the center of anything.

When Alaska and Hawaii joined the Union in 1959, the center of the country moved northwest into western South Dakota. The USGS gives it as 44°58′ N, 103°46′ W, without naming a town, because there is none at the spot. The nearest city is Belle Fourche, about 20 miles south.

The National Geodetic Survey has a survey disk named CENTER (PID PU2386) in Butte County, set by the Coast and Geodetic Survey in 1962 and stamped "CENTER 1962". Its published position is 44°58′02.08″ N, 103°46′17.60″ W. It is a triangulation station, not an official designation of the center; the USGS's caveat that no agency has monumented a center still applies.

Belle Fourche has its own Center of the Nation monument in town, which is where most visitors go. It is a symbolic marker; the computed point is about 20 miles to the north.

Between those two dates there was briefly a 49-state center. With Alaska but before Hawaii, the USGS puts it near Castle Rock, Butte County, at 44°59′ N, 103°38′ W, only a few miles from the 50-state point.

A geographic center is the centroid of an area: the average position of every square mile of it. The USGS is blunt that there is "no generally accepted definition" and no completely satisfactory method, and it lists the reasons: the curvature of the Earth, large bodies of water, and irregular surfaces all change the answer. Its published centers are labeled approximations.

Three choices move the result:

1. Flat or round. A cardboard cutout is a map projection, and every projection distorts area somewhere. A modern calculation works on the sphere or ellipsoid instead.
2. What counts as area. Including or excluding the Great Lakes, coastal waters and the Chesapeake Bay shifts the center by miles.
3. How detailed the coastline is. A generalized outline drops thousands of small islands and inlets.

To see how much this matters, we computed the spherical area centroid of the same generalized Census state polygons (2017, 1:10,000,000) that the site's maps use. The 48-state result is 39.76° N, 99.01° W, about 23 miles west of the Lebanon figure. The 50-state result is 44.76° N, 103.98° W, about 18 miles from the published 50-state point. Agreement within about 20 miles is good for a 1918 estimate, and the difference shows why the USGS treats every center as approximate. The crosses on the map above mark our results.

A centroid is not always inside the shape. For a crescent or a ring the average position can fall outside it entirely. That does not happen for the United States, but it is why the "center" of a coastline-heavy state can land in a bay.

The Census Bureau's mean center of population answers a different question: where would a flat, weightless map of the 50 states and D.C. balance if every resident were a weight of identical size? For 2020 that point is at 37.415725° N, 92.346525° W in Wright County, Missouri, 14.6 miles northeast of Hartville. The Bureau calls it the most western and southern mean center in the nation's history.

The center has moved west at every census since the first one, and south since the mid-20th century. In 1790 it was in Kent County, Maryland, 23 miles east of Baltimore. Since then it has traveled 885.9 miles, according to the Census Bureau:

The median center of population is the crossing of the north-south line and the east-west line that each split the population in half. In 2020 it was in Patoka Township, Gibson County, Indiana, between Princeton and Fort Branch, about 269 miles east of the mean center. The two differ because the mean is pulled by distance: a million people moving from Kansas to California shifts the mean west, but if they stay on the same side of both median lines, the median does not move at all. The Census Bureau's own documentation uses this example.

"Center of the United States" can refer to a few more points:

• Center of North America. The USGS puts it about 6 miles west of Balta, Pierce County, North Dakota, at 48°10′ N, 100°10′ W. Rugby, North Dakota, has a well-known marker for it, although the USGS location is a few miles away.
• State centers. The USGS also published the geographic center of each state, usually given as a distance from a nearby town, for example 5 miles northeast of Ames for Iowa or 15 miles northeast of Brady for Texas.
• The center of a group of places. The midpoint of your customers, your family or a list of cities is a different calculation again: the average of a set of points rather than of an area.

The geographic center finder computes the center of any set of addresses or coordinates. It converts each point to a 3D vector, averages the vectors and converts the result back to latitude and longitude, which avoids the errors of averaging latitudes and longitudes directly. It is a close relative of the Census Bureau's mean center of population, with each place counted once instead of each person.

For two places, the halfway point tool finds the midpoint along the great circle between them. And to read off the coordinates of any spot on the map, including the markers in Lebanon or Belle Fourche, use the latitude and longitude finder.