I don't mean to sound like a arsehole here.. , but the mother road starts (or ends) in Chicago, which in not on a coast...unless you consider the lake front coast.
I believe 2lane lives very close to the original mother road through Joplin, and I live just off the new Missouri 66.
Here is another website...http://www.rideandflytours.com/route66.php
The classic Route 66 was east to west, taking midwesterners out west to the golden state of California, seeking a new life and opportunity. Lots and lots of farmers / "Okies" (from Oklahoma, of course) made the trip. See also Steinbeck's
Grapes of Wrath for the classic telling of the story of the fictional Joad family. My favorite period account novel. There are chapters between the chapters which really capture the essence of this era.
So anyway, start in Chicago. I think Ogden Ave. was the original origin of the highway & unless the west side has changed a lot in the last 15 years, that first 20 minutes of the ride are gonna be through a rough part of town. Then it's smooth sailin' . . . .