If anyone is crossing WashingtonState on I-90, a good side trip is
from Moses Lake, Wa. ( about mid way between Spokan and Seattle )
take a side trip north to Grand Coulee Dam.
The Dam is a great destination if you have never seen it.
Also, the road runs thru whats called the " Dry River Valley. "
Check this link: http://www.google.com/search?hl=en&=Dry+Falls
The Geological formations here are really Fantastic scenery
This valley was formed by a Massive Floods, about 10 to 15,000 years ago.
There is No River flowing thru it now.
Or, from Spokan, take Hwy 2 too Grand Coulee Dam, then south on 155 to Coulee City heading badk to I-90.
Also, if you are in Seattle, and want to take the Long, Slow Sceinic Route to Calif. ( Assumeing you are not in a hurry )
From Port Angeles Wa. on the Northern Coast, take U.S 101, west to Forks Wa. then follow the Coast Route U.S. 101 all the way to San Franscisco.
( If you are an Aviation Buff! be sure to visit the Old Naval Air Station at Tillimook Oregon (Aviation Museum ) and a side trip to McMinville Or. to see
the Spruce Goose if you have never seen it )
This drive would take about 3 days, to a week depending on how many stops you want to make.
Be Carefull!! you will see lots of Deer !!