Route 66

66 doesn't really exist anymore.

Chicago to LA is 30+ hours in the car. Mainly nondescript highways now that bypass the original 66. And a lot of the stops that still exist are tacky tourist traps. Sometimes 7-8 hours driving of absolute nothingness.

Not sure 30 hours driving is worth it to see St Louis, Tulsa, Gallup, Flagstaff et al.

If you're planning a road trip, Highway 61 is much shorter (14 hours ish) and with a detour here and there you could see Chicago, Louisville, Nashville, Memphis, Clarksdale, Vicksburg, Natchez, Baton Rouge, New Orleans. And it gets warmer and cheaper as you head south.

Or just fly into Nashville and do it from there which is about 8 hours driving combined. So over 2 weeks or so you've a great holiday. Still maybe my favourite I've ever done.

Another cracking drive is the coastal route from Washington DC to Savannah which I've done recently. 14 hours ish over 2 weeks. Apart from the places highlighted, loads of small little towns to stop in on the way.