When most people read the title above they hear, "What is my favorite national park?" Well, there is no accounting for taste.
In fact, national parks are not beautiful at all -- and remember, you read that here! They are merely freakishly big, vertical, or red.
"Beautiful" means variety, balance, harmony, and utility: the color green, productive agriculture, soft hills with womanly curves, spirited creeks, barns, wildlife and herds of domestic stock, not many people, and trees. A few rocks are tolerable. And that is what you see in the Palouse of eastern Washington, especially near its border with forest land.
Driving through this land on a semi-rainy day, I lusted for a drone to photograph it. The three-dimensionality might get washed out if photographed from the highway. Sunrise or sunset, and partly stormy skies!
I managed to camp in the national forest near Moscow, ID with my first ATT signal, as a newbie customer. Idaho actually puts gravel on their forest roads, so the rain didn't render me immobile. Good grief, I wore a light rain jacket and a baseball hat instead of my canonical Henschel Australian Breezer.