Travelling across the good ole USA

Seems to me there's not enough info here to afford any sort of intelligent guess as to what would be most useful to the OP, beyond "any time you've got the time is a good time to go." Every route from Maryland to Washington (state), even ones passing through the Arctic Circle in Canada as well as along the southern Mexican border have things to see and do, take varied amounts of time, and work best in certain seasons, as well as depend on the vehicle being driven. Some possible routes argue against the attempt if your rig is 65 feet long, or if it's powered by hydrogen or depends on Tesla Superchargers.