Almost all of the western most states in the lower 48 have at least one national park. Washington has Olympic National Park and more, Oregon has Crater Lake, California has Yosemite and more, Nevada has Great Basin and part of Death Valley, Arizona has the Grand Canyon and more, New Mexico has White Sands and more, Utah has Arches and more, Colorado has Rocky Mountain and more, Wyoming has Yellowstone and Grand Teton, and Montana has Glacier.
A major part of the western road trip concept focuses on America’s greatest national parks, and the landscape easily works for it. So why is Idaho national park free? Craters of the Moon is a national monument, so they have that, and a sliver of Yellowstone is technically located inside the Gem State, but why doesn’t it have its own, complete national park when it seems like there are plenty of places for one?