Boise to Denver
I-84 to I-80 to I-25, roughly 830 miles across southern Idaho, Wyoming's high desert, and the Front Range.
I-80: Salt Lake City to Cheyenne
About 440 miles of Wyoming high plains and wind. One of the loneliest full-day stretches in the Lower 48.
I-90: Seattle to Bozeman
Roughly 700 miles over Snoqualmie Pass, across eastern Washington and the Idaho panhandle, into Montana.
I-40: Albuquerque to Oklahoma City
About 540 miles of the old Route 66 corridor across eastern New Mexico and the Texas panhandle.