Route 66 is the "Main Street of America," heralded in song and popular culture. It took a maze of different routes through St. Louis before slashing diagonally across the "Show-Me State" through the beauty of the Ozarks. In between, there are classic motels, diners, tourist traps, and gas stations bathed in flashing and whirling neon lights. Natural wonders include crystal-clear streams, majestic bluffs, and wondrous caverns. Roadside marketers concocted...