The Crossroads of the West is Green River, Utah. They say so themselves. And at the crossroads is the John Wesley Powell River History Museum. It is a hidden gem worth stopping for; just jump off I70 and take Business 70 through town.
As everyone knows, J. W. Powell was a one-armed Civil War veteran who led the first expedition through the Grand Canyon. Prior to his expedition, the Colorado River appeared only intermittently on maps. He filled in the gaps.
At the museum: