Blah... you don't want to go to DC... nothing there but big marble buildings and even bigger political ego's...
Actually it's a pretty good place to start... but I would make sure to get up to NYC also, and then head West.
If the idea is to see the country, I suggest rail. There used to be an Amtrack ticket that let you get on and off pretty much anytime you want. It's fairly expensive but gives you a lot of options. Either that or rent a car, although a cross country point to point (non-roundtrip) will REALLY cost you.