I have taken this drive through Idaho and Montana several times. There isn't much there, other than open road, green space, and some mountains. As you are leaving Washington going east, there is a Wild Horse Memorial that sits on top of a giant hill. It's really a cool thing way out in the middle of nowhere.
On to Idaho . . .
This is a BEAUTIFUL (again out in the middle of no where in Idaho) memorial for miners who were killed in the worst mining disaster in Idaho. (Sunshine Mining Disaster Link). If you look closely to his hat, there is a light on it - that light always stays on.