The small, but highly recommended, Oklahoma Route 66 Museum is in Clinton, just off I-40 in western OK. It is relatively expensive, but well worth the cost, especially for anyone who can't remember American highways before Interstates completely changed our travel habits.
And there is a very nice city park campground in Sayre, OK, 40 miles west of Clinton. It is a CCC-built park with a swimming pool, golf course, and ball fields. It has 80 or so shaded, pull-through and back-in, electric-water campsites with a dump for about $10/night. It is our only recommended choice for a campground when we are traveling I-40 in western OK.
Have fun exploring!