A lot of the Cascade range is basalt, and you don't need to cut down very far to expose it. A result is that most waterways in Oregon have revealed a lot of basalt around them, at least in the mountains.
Yep, there's a ton of it to be found especially in the Columbia River Gorge. For anyone not hip to Nick Zentner, allow me to introduce you to this national treasure...
It's rare to have basements where I live in Bend, because it's all lava rock right under our feet, which is really expensive to remove.
Climbing on columnar basalt is interesting. Vantage / Frenchmans Coulee (2 hours or so east of Seattle) has a bit of a bad reputation but some of the routes are decent.
Pilot rock outside of Ashland you can even hike to the top