I'm not in the US but if i was going to do a tour up there, i'd find some of the most historical places & ride there.

Can you bike near on the Appalaichan (sp, sorry) trail? I know there's a nice YHA near the start....

Follow the underground railroad route?

Sorry to be vague but what about on the west coast? (can't think of the two explorers at the mo but the ones that opened up the west...)

Have fun!