Long before Beat Generation novelist Jack Kerouac immortalized the road trip or Americans got their kicks on Route 66, cross-country drivers had to navigate a confusing network of colloquially named thoroughfares to reach their destinations. Like pioneers of yore, motorists in the early 1910s could follow the National Old Trails Road—a transcontinental route between Baltimore, Maryland, and Los Angeles, California, stitched together from existing roads and historic wagon-train paths such as the Santa Fe Trail—or the Lincoln Highway, which connected New York City and San Francisco. As cars proliferated, so did demand for better roads. Countless automobile clubs, auto trail...