During it's lifetime Route 66 saw many realignment which were necessary in answer to automobilistic progress and increasing traffic thru the continent, esp. during wartime. Military transports needed improved roads to carry heavyweight long vehicles to the pacific coast. When post war tourism or later on commercial traffic left Route 66 congested, further improvement was made to the road. Eventually Route 66 was decommisioned in favor of the Eisenhower's interstate system.
Every realignment shortened the way from Chicago to L.A.
There are 4 distinct timely partitions which are covered with the atlas maps and depicted in different colours.
Clicking on the link will give you examples of historic Route 66 mileages as of 1926, 1939, 1947
|The 1920s alignment (old 66)|
|The 1930s alignment (classic 66)|
|The 1940s alignment (pre-interstate 66)|
|The final alignment (interstate 66)|