Hint #2: The lake is more or less north of where I took the picture; this is an easterly view from a little farther up the same trail:


Hint #3--to reach this place from Portland, you drive east about 6 hours on a US highway that starts near Seaside, OR, goes through Portland, follows the Snake River to Jackson Hole and ends up following the Oregon Trail route to the highway's end in Ogalalla, NB. The mountains and lake in the photo are south of this highway.

Surely somebody on this board has been there!