I just re-read your post and see that you're looking for a more northern rather than southern route. I'm not sure why you'd go through Kansas, as the...
The most direct, mostly Interstate route option is fairly simple. Just take I-44 down to Oklahoma City and then I-40 west to Barstow CA and use I-15...
I love the Ppacific Northwest, but what I have appreciated most about it is that other than perhaps Olympic National Park (which does have a section...