as our old RV (and us) don't like crossing mountains... what is the lowest altitude going from the west coast to the east coast across the mountains. i was told that I10 is flat but elpaso is 4000 f...
I-10 crosses the Contential Divide in New Mexico at 4585 ft. It is a slow climb and does catch you by surprise when you get there. I-10 in Arizona does get above 5000 ft.