Missouri
The Ozark Highlands of southern Missouri, which Route 66 crosses in its 300-mi (485-km) journey between Illinois and Kansas, are about the only significant hills the road crosses east of the Sandia Mountains in New Mexico. This plateau region, though not by any means alpine or breathtaking, is visually dynamic in a way the broad flatlands of Illinois or Oklahoma rarely are.
Though the I-44 freeway has replaced the old road all the way across the state, there are many signs of older alignments, and just about every interstate exit drops you within a moment’s drive of the Mother Road. Missouri also holds some great old motels and one of the greatest of the old Route 66 tourist attractions—Meramec Caverns, an extensive set of limestone caves offering the most over-the-top underground tour you can take.