You can see two giant arrows, a Route 66 icon, as you travel west or east on I-40 between Flagstaff and Winslow.
If you go:
Pull off at Exit 219 on I-40 for a photo. The old trading post remains closed, but restoration is underway. You'll want to pull over onto the shoulder east of the trading post almost as soon as you get on Frontage Road as the parking lot at the trading post is blocked off. Use caution when parking and getting out of your vehicle. RVs should continue east and enter I-40 at the next exit rather than turn around.
Links:

Old Route 66
Exit 219 on I-40
Twin Arrows, Arizona USA