Here are some resources for Route 66 I found on the Oklahoma Dept. of Transportation web site:
Intro with legislative changes to the route:
http://www.okladot.state.ok.us/memorial/route66/index.htm
Construction history:
http://www.okladot.state.ok.us/memorial/route66/route66const-hist.htm
Route 66 maps. Not just down to the county but down to the section! These show early, middle and late alignments.
http://www.okladot.state.ok.us/memorial/route66/route66maps.htm
Route 66 photo gallery:
http://www.okladot.state.ok.us/memorial/route66/route66.htm
Parsa
I forgot this page. it's really cool:
A Chronology of the Construction History of Route 66 in Oklahoma
http://www.okladot.state.ok.us/memorial/route66/consthistory/index.htm