Well, they identified themselves as cowboys, not as sheepherders.
Having grown up in the west and worked a memorable summer herding cattle in rugged high range country, living off the land in a remote log cabin w/out electricity and other amenities, I can say with some knowledge that if they could have found work with cattle, they would have not have herded sheep. Sheep herding was work done by immigrant labor, primarily Basques at that time. That's how low their status and prospects were, that they, American boys, had to settle for herding sheep.
[And, yes, I have notes for a story based upon that summer.]
Proulx lives in the country she wrote about: her story was keenly observed and thoroughly researched. It brought back s-o-o many memories of place and period.