I live on the very western end of the east- west one .. the linked route goes down the coast first,
then Over the Cascades via Eugene..

Louis and Clark Route heads upstream on the Columbia River valley .. to St. Louis MO.

river gorge cut thru the Cascade mountain range as it was forming..

Other routes you climb over that mountain range..
(Way south its a lower rise but summer is dangerously hot to be riding .. 40C + is common.)

the Jeffersonian Guys did it both ways, Of course.. BTW , the US West, It's bigger than you Think..

And the basin and range is a lot of wide open horizons .. carry water by the 10's of Liters + .

the tire dip in the Pacific at Sunset beach
as bookends with an Atlantic tire dip on the other end is something Many Do.