Thanks for the additions
Gardyloo, great to get some local perspective! The 'What in the Sam Hill' expression we were familiar with even from across the pond (although presumably due to exposure to US media - I can only imagine it in an american accent). Our guide explained both that saying and Hill's central involvement with the original Columbia river highway, but we didn't hear much about his other architectural pursuits, and it seem there were many! We did learn a lot more on the tour than I've attempted to recount here - I'd definitely recommend it for out-of-towners, although some familiarity with US history would probably add to the experience.
We passed the sign for Portland Women's Forum Viewpoint - from your picture definitely a shame that a stop here wasn't included, and indeed more time at any of the locations would have been appreciated. But even with our limited selection of stops it was some eight hours round trip from Portland, of which at least half was probably spent on the road, so I guess the organisers have to be selective. Having now got an overview I'd love to return with a hire car (and someone to drive it, since I can't!)