Google maps is not a reliable source. Their bike directions are in beta phase and will lead you miles out of your way. They also don't identify gravel so you can run out of pavement unexpectedly. Most states now have bike routes available from their DOT for download. Here's a couple posts I put on my blog with my experience:

http://simplecycle-marc.blogspot.com...ngled-way.html
http://simplecycle-marc.blogspot.com...revisited.html

Marc