What story had Ethan heard about "- man over the mountain"?

From the text:

He knew a case of a man over the mountain- a young fellow of about his own age- who had escaped from just such a life of misery by going West with the girl he cared for. His wife had divorced him, and he had married the girl and prospered. Ethan had seen the couple the summer before at Shadd’s Falls, where they had come to visit relatives. They had a little girl with fair curls, who wore a gold locket and was dressed like a princess. The deserted wife had not done badly either.