Lowest altitude route

Not sure if this is the appropriate thread: newbie.

I know GE will plot the altitudes for a given path. But can it be made to determine the path itself for the lowest altitudes between 2 points (on highways)? I'm trying to determine that for a coast-to-coast trip from Virginia to Seattle for medical reasons. 

All elevations in Google Earth are approximate only. They are based on data from the 2000 Shuttle Radar Telemetry Mission and could have as much as a 30m+ error.  That said, if you plot a simple line between point A & point B. Save it to my places for reference. You can right click on the line then click "Show Elevation Profile", a trace of the line at ground level will present itself at the lower half of the view window. Alternatively, instead of manually tracing a road you can use the "Get Directions" between two points and right click the resulting route line and select "Show Elevation Profile".  Roads themselves cannot be directly selected.

B66