IL, MO, NM, AZ.
If anyone has seen the Disney/Pixar movie "Cars" it is based on Rte 66 and all of the small, often ignored and financially suffering towns that were once booming little tourist attractions until the Interstate Highways came along and bypassed them.
The National Scenic Byway program was established, in part, to help convince travelers to get off the superhighways and explore these smaller towns and all they have to offer.