I saw a guy riding his bike on the shoulder of I-5 in Salem, OR a few nights back. I don't know if it legal or not, I know one could walk on I-5.
My cousin did Atlanta to NYC two years back, and had to do country roads most of the way up. He was almost hit a few times.
This summer I am planning on heading east to Virginia, plane or drive, then ride a bike back to the west coast.