
Originally Posted by
AZBuck
Welcome aboard the RoadTrip America Forums!
I did a quick check of both internet resources and topographic mapping routines and of your two best choices, the maximum elevation I could find for I-90 was 4,725 feet at Lookout Pass on the Montana/Idaho state line, while the highest I found for I-10/I-5 was 4,310 feet at Siskiyou Summit in northern California. For the few hundred feet difference the northern route saves you around a thousand miles of driving. I-80. I-70. and I-40 all reach elevations in excess of 7,000 feet.
AZBuck