I went to this in 2006. Good turnout as they shut down about 12 blocks of downtown Springfield for the event.
It looks like there is a new "promoter" this year as the website is not as good as in the past. There is a car registration fee, but the event is free to the general public (at least it used to be).
There are a lot of Route 66 events in the area.
If you go, you've got to have a Cozy Dog at the Cozy Drive In and a donut at Mel-O-Creme.
Also if you have time, there are a lot of Abe Lincoln sites in town.



http://www.familyevents.com/event/87