It's a map of the number of people on each county government's board of commissioners.
I was actually kind of suprised at how little it's based off population. Also, lol at Webster for having one commissioner for every 450 people.
How is the size of the commission determined?
In Texas, all counties have 4 county commissioners, including Loving County which has fewer than 100 persons, and Harris which is the 3rd most-populous in the country with about 3.5 million.
Commissioner precincts (districts) have to be equal population, but each commissioner has some administrative jurisdiction in his precinct. This means that in rural counties, each precinct might include part of the county seat in order to meet the equal population requirements, but then include large swaths of the county so that each commissioner has some roads to maintain.
Even in Harris County, there is some attempt to give each precinct some unincorporated areas so that they can develop parks and build roads.