Another of the great geological feature adventure stories (with, e.g., Lorna Doone, The Island Stallion; also some pirate novels; when even the deus ex machina is inert, you know you have some pulp characterization...)
There are a few places that really do have geological features as astonishing as any building; and the parts of the Southwest that Zane Grey wrote about are among them, and his writing is best when evoking the drama and sentiment of the landscape. The Wild West romance-and-real-estate plot makes a lot happen (all suitable for a Firefly episode) but the landscape is the charm; and the horses.
There are two female proto-heroines; proto- because they aren't very efficacious, as far as the plot goes, but heroines because they are courageous and skilled. I take what I can get.
One of them is a Mormon heiress, under social and economic duress by the elders of her region. There's reflexive anti-Mormon fulminating, all justified by their treatment of women. From my vantage the Mormons in this novel look not much worse than the non-Mormons. Most all of the non-Mormon men with speaking parts happen to be individually virtuous, but it's obvious from one subplot or another that women outside the region are also at considerable risk. I did very much like the consideration of the divided loyalties of Mormon women, who perhaps would like the heiress to be left alone, or failing that to stop rocking the boat, but who abandon her when the chips are down. They come across as weak but not venal. It's not where you expect a quiet little argument for sisterhood in the face of oppression, but again, I'll take what I can get.
Project Gutenberg etext 1300, Riders of the Purple Sage
So wrote clew in Fiction (20th c.).