Perfect Oregon State Park Campground
Just 45 minutes outside of Portland, and near the town of Estacada, is Milo McIver State Park, which I consider to be a quintessential Oregon State Park: lots of huge evergreen trees, large campsites, plenty of hiking areas and places to explore including a river.
There are two main loops in the main campground. The larger has 44 or so RV campsites, which can also be used for tents, plus a bathroom with flush toilets and hot showers. Nearby is a smaller loop of 9 or so tent-only sites that seem a bit more private.
We went during a vintage trailer rally, which was a ton of fun, since you could walk around and see everyone's trailers. There's also a Frisbee golf course and some fields to explore as well.
Overall, a nice, fun campground near Portland with larger sites and just enough to keep you busy.