I’m planning a cross country road trip across the US. What do I definitely need to see?

I like state and national parks more than cities.

thank you!

There are so many wonderful things to see it is hard to list them, but if I had a lot of time and money wasn’t an issue I would see Acadia NP (Maine), Boston (the history), NYC–just to say I’d been, The Smokey Mountains–very beautiful, the St. Louis Arch (Gateway Arch), Rocky Mountain National Park, Carlsbad Caverns, The Grand Canyon, Yellowstone, Yosemite, and then San Diego (great zoo).