answer:There’s no best. The FANTASTIC possibilities are endless. So here’s one: San Diego to Seattle From the Mexican border to the Canadian. Include some inland trips. You can see desert, snow, mountains, the highest (Mt Whitney 14,505 ft) and lowest (Death Valley −282 ft) points in the 48 states, huge cities, tiny towns, Hollywood and loggers and truckers and hipsters. LA, San Francisco. The redwoods. Big Sur. Marin county. And a thousand things I cannot think of at the moment.