Clayton, which lies flat on the high prairie at an elevation of 5,000 feet, seemingly grew up out of nothing. Downtown is sleepy and sunny, with the old-fashioned retro-veneer typical of little Western towns. It's nowhere near an interstate and so lacks the scads of ubiquitous chain properties found in Las Vegas and Raton; mom-and-pop-owned shops dominate. This town of about 2,300 bills itself as the carbon dioxide capital of the world, but the carbon dioxide here isn't hanging in the air but rather underground, embedded in sandstone southwest of town. Cattle graze on the many ranches around Clayton, which is the seat of massive and sparsely populated Union County, which at more than 3,800 square mi is larger than Rhode Island and Delaware combined.