Most will agree that the geographic center of Texas is in McCulloch County. Exactly where is open to question.

Texas Geography from Netstate provides some explanation and references that help clarify the issue. They describe the Geographic Center of Texas as:

The geographic center of Texas is located in McCulloch County, 15 miles NE of Brady.
Longitude: 99° 27.5'W
Latitude: 31° 14.6'N

That sounds definitive until you look at that Latitude/Longitude on a map and find that it is not 15 miles Northeast of Brady.

It is actually Northwest of Brady a couple of hundred yards off CR 152 just north of the community of West Sweden as shown by the purple pin in the upper left corner of the map below:

To confuse matters further, there is a roadside marker about 20 miles northeast of Brady on Highway 377 describing the Center of Texas as being "Five miles northwest ...". But, five miles Northwest of the marker is not anywhere close to either being 15 miles NE of Brady or at 31° 14.6'N, 99° 27.5'W.

We cited Netstate as a reference above because they have delved into these inconsistencies and offer a plausible explanation. Quoting Netstate:

NETSTATE provides coordinates and location descriptions that are intended to pinpoint the "geographic center" of each of the States of the United States. This information is/was obtained from the United States Geologic Survey (USGS). We have received numerous questions regarding this information including complaints that the coordinates don't align with the location descriptions. In response to the questions we have received, we contacted the USGS. Essentially, we have tried to get information about the methodology used to calculate the coordinates and the location descriptions.

We have been unsuccessful. The USGS has taken the position that the source for this information is unknown and that there is no official definition for a geographic center and, therefore, no official methodology for determining a geographic center.

The USGS has removed virtually all of coordinate information that they provided online, but they still maintain a list of location descriptions.

The following was quoted from the USGS web site on November 6, 2007:

Because there is no generally accepted definition of a geographic center and no completely satisfactory method of determining it, there may be as many geographic centers of a State or county as there are definitions of the term.

The geographic center of an area may be defined as the center of gravity of the surface, or that point on which the surface of an area would balance if it were a plane of uniform thickness.

Curvature of the Earth, large bodies of water, irregular surfaces, and other factors affect the determination of center of gravity.

In determining the centers of the States, islands adjacent to their coastlines and large bodies of water were excluded.

The geographic centers and positions listed below should be considered as approximations.

NOTE: "Positions" noted in the last sentence above have been removed (except for Alaska) from the information provided in the USGS Geographic Centers table.

The overall conclusion is that the pin on the map above shows what was the official USGS location until 2007. Now nobody really knows exactly where it is. This is progressive progress.