500
"66 is the path of people in flight, refugees from dust and shrinking land, from the thunder of tractors and shrinking ownership, from the desert's slow northward invasion, from the twisting winds that howl up out of Texas, from the floods that bring no richness to the land and the streal what little richness is there"
-John Steinbeck, The Grapes of Wrath
Why did people travel on Highway 66 - according to this.
Fleeing the bad land to the good land