Several weeks back I took myself on a fine little nature walk at a park very near an interstate highway (that's one clue).
There were big-leaf maple trees.
But this photo has the real clue:
Yup, oak leaves. It's estimated that the oak savanna habitat that once covered 500,000 acres in the Willamette Valley of Oregon has been reduced to about 1% of its original range. But there are several pockets where you can see this habitat preserved. Any local folks have guesses as to which one I was at? Here's your last hint, and it's a big one, if you've visited the same place: