There are only a few sections of the US66 still remaining. CA-AZ-NM have the most sections still there. Of Course ROUTE 66 only goes between Chicago and Los Angeles. For the most part Route 66 follows the now I40 route once it starts going East and West..
The only part I have really observed good is in the FLAGSTAFF/WILLIAMS AZ areas... Everyone needs to have their picture taken standing next to one the ROUTE 66 historical road signs.
The Meteor Crater is the breath-taking view and has an outstanding Information center but once you see the big hole in the ground not much else for us to do there hehe... Petrified Forest is another wonder to see. I also fell in love with the Wupatki Ancient Indian Ruins & Cliff Dwellings North of Flagstaff. especially just before dark when you can look to the EAST when up on one of the high ruins and see the PAINTED DESERT starting to change all of its colors.
If you got time to kill the Grand Canyon would be be the place to see... Also in and around Flagstaff including SEDONA and other high country places blew us away for years of going there - Always see something new when we visit. The RED ROCK canyons blows us away hehe...
Not sure when you are going on the trip by HIGHWAY 89A is undergoing alot of work and may be closed in sections around SEDONA. Scheduled work to road and the AZ FIRE has done a big number on the road.
If you end up camping in FLAGSTAFF over night be aware that the railroad that goes through there is active with trains about every 5-miunutes all night long... Might want to get off the main drag there when spending a night or two.
Roy Ken