Why did Route 66 have so many iterations and reroutes when Interstate routes rarely get moved?

Question

Why did Route 66 have so many iterations and reroutes when Interstate routes rarely get moved?

In: Other

Answer 1

Route 66 is part of the U.S. numbered highways system, which is distinct from the interstate highway system. The U.S. numbered highways system is in fact the precursor, and can be treated as the result of the first attempt to formally define a national highway system with uniform markings (previously, these highways were designated/maintained by local private entities). As a result, it did take a bit of trial and error to determine the various routes, and other changes occurred later to better facilitate traffic.