Also, on the edge of the Portland Metro area is the
Evergreen Aviation Museum, home of the famed Spruce Goose -- if that's your kind of thing.
Here's a pic of an SR-71 there that I took some years ago:
And here you get a little idea of how stinkin' big the Spruce Goose really is:
Definitely recommended, if you have the time and inclination for such things.