For settlers migrating westward, it was uphill all the way to the Great Divide, and on the other side it was an easier downhill run to (they thought) a better place. (Although many of them wound up in California despite what they hoped for?)

While I don't have any historical references, it's a reasonable metaphor for the "stuggle through life" but when you "cross the divide" it gets easier (regardless of which downhill direction you take to wherever you're going to end up?).

There actually were/are TWO "divides" in the US. The Appallachian divide is reached from sea level to around 3,000 to 6,000 ft (guessing a bit) elevation, but passes through the second Rocky Mountain divide run up to 8,000 to 10,000 ft MSL on some routes.

After crossing the Appalachians, you'd descend to about 1,000 ft MSL, followed by a relatively easy 300 to 400 mile ascent across a rising praire, to the "mile high" area where the Rockies start up.

Lots of people settled in the middle plains because of anticipation of how difficult it would be to cross something as high as the Rockies (up to 2,000 ft higher than the other one they'd already fought with) without considering that they would be starting from 5,000 or more ft on the "high plains" when they hit the second hard ascent.

Another vaguely associated term from the same era was "He/they saw/seen the elephant." Worth discussion, perhaps, if there's interest in what the migration and settlement were like, although some others may know the stories better than I do.

John