When you name a county (or equivalent) of Texas, all Texan counties within 100km of its center will also be filled in.
Distance here is the centre-centre distance using the latitude/longitude geographical centres provided by the U.S. Census Bureau. (This means for a big county, its borders may not get activated)
There is a Houston County with the City of Crockett as the County seat, not to be confused with Crockett County in Western Texas. But Houston County way less known than the City of Houston in Harris County. I think cities with the same names as some counties being in different counties is goofy.
/t