WE WERE leaving Kingsport, that once-proud “model city” in the Tennessee hills that had slid into obscure mediocrity, and heading to California, the land of opportunity.  We piled our belongings in the back and on top of our Ford Fiesta, and headed west on Interstate 40. We traced the route traveled in harshness and hope by so many families searching for new opportunities, when the earth had dried up and the economy had gone sour. Across the dusty plains of Oklahoma and Texas and past the barren red rock of New Mexico and Arizona they went, and we followed. Where the migrants of the 1930s coaxed aging trucks along two-lane roads, we pushed the speed limit on the four-lane highway. But the small car laden with our worldly goods bore an odd resemblance to the broken-down jalopies with somber-faced families that are seen in aging photographs.