At the top of this page is a drawing of Route 66 with the main towns that lay on the route: http://www.historic66.com/books/map-8statemaps.html
Route 66 now lies alongside Interstate 44 to Oklahoma City and then Interstate 40 to Santa Monica.
The most famous song version is Nat King Cole’s:
And then there’s St. Louis’s own Chuck Berry, for a rock version (he mispronounces Barstow, grrr):
And then it was redone in Cars by John Mayer: