I-15 between Las Vegas, NV and St. George, UT is worth driving. The only town of any size you will go through is Mesquite, NV, a golf-course studded, well-tended retirement community near the Nevada/Arizona border where Ruth scored her only casino jackpot. Shortly after you pass NV exit 112, the Interstate begins to follow the Virgin River headed south from there to Lake Mead. The road stays close to the Virgin for many miles even as the Interstate enters a canyon carved by it. That canyon lasts almost all the way through Arizona to St. George, a boom town just over the Utah/Arizona border.
I love the less than 60-mile drive on I-25 between Albuquerque and Santa Fe, NM. Because Albuquerque is 5, 312 feet and often hot like a desert and Santa Fe is 7,199 feet above sea level and cool like a mountain community, drivers and passengers have a real sense of climbing quickly toward another world. Many choose to skip I-25 and instead take The Turquoise Trail to Santa Fe. Also called State Road 14, the Turquoise Trail is definitely a scenic byway and gives access to a really weird attraction called Tinkertown, which probably won’t be around much longer. If you choose the Interstate, know that it follows old Highway 66 of song and myth.
I-87 north through the Adirondack Mountains to the Canadian border and Quebec is an increasingly scenic mountain drive with impressive lakes at both ends. At the south end you have Lake George, which is also a town, and up north the Interstate is very close to Lake Champlain and all of its bay offshoots. Knowing locals would probably advise you to do this only in the summer when you’re on vacation.
I’m a big fan of I-35 between Oklahoma City and Marietta, OK because it takes you through the relatively unknown Arbuckle Mountains. Not especially tall and topping out below 1,500 feet, some find the Arbuckles the most serious mountain range between the Appalachians and The Rockies. I, however, and for personal reasons favor the Ozarks, Ruth’s ancestral home. Turner Falls Park in the Arbuckles south of Davis is worth seeing. The only semi-large town on this Interstate is Ardmore, OK with about 25,000 citizens but not much to do. By the time you get there, you’re about 10 miles south of the Arbuckles.