The metabolism of travel changed more in the last century than in the previous half-millennium, a stunning transformation triggered by American wanderlust. In less than 100 years, the U.S. mass-produced the automobile, invented airplanes, freeways, motels, even sent men to the Moon. Travel grew ever faster and easier. Above all, it was democratized — enabling millions to explore distant lands, or see their own more fully. At the start of the 20th century, only people with extensive disposable income and time to spare could enjoy leisure travel. By the century's end, journeys took hours, not days, and mass travel — especially brief air flights — became the new normal. Along the way, ocean liners broke speed records, aerodynamic trains roared down the tracks, stylish boat-plane clippers evolved into jumbo jets. Whether aboard high-speed locomotives or ships, jets, or Greyhound buses — or when setting their own schedule on the open road — Americans demanded ever greater mobility...