Idea that won't leave my head now that I put these two words together:

Idea that won't leave my head now that I put these two words together:
Cowboys of Carcosa

Back east there are cities, steam trains, and other modern wonders. Inland to the west are farms and rural communities as far as the eye can see. Then the mountains. Massive, skyscraping, un-passable mountains. But why go over when you can go through? Dynamite has done the work and now settlers are moving west, bringing the steam engine through the tunnels. The land on the other side is expansive and fertile. Herds of huge reptiles (some very dangerous!) share the plains with giant bison and mammoths. But, scattered here and there are ancient, abandoned cities of black basalt. What lived here in prehistoric times?

You're in luck buckaroo. The rails are hiring scouts. And the ranchers want some of those big three-horned lizards for steaks. Rumors say the cities are full of gold. Yep. A man could make a name for himself in the west.