I live in Seattle and almost every single road I drive on is at least concrete base.

Even if I couldn't tell for other reasons, I've seen enough sections replaced for water or gas line maintenance; I've never seen one without concrete, from my side street all the way to the freeway.

Maybe that's a Washington thing, then. In the Portland area it's nearly all asphalt, or asphalt-over-concrete. Concrete is terrible in places where it rains a lot, which is one reason I'm surprised you'd find so much of it in Seattle. We have porous asphalt that never has any standing water even in a downpour. At least when it's maintained, which isn't always a guarantee on some lesser used roads.

Older Seattle area roads tend to be concrete; newer roads are more frequently asphalt. It was definitely very popular here in recent memory — I could name tons of concrete Seattle roads off the top of my head — but my impression is it is no longer as popular in new construction.

There's some real old roads that are bricks under asphalt. That's a trip. Some of the real steep stuff like Bell or Blanchard at Western, IIRC.

PS if you like brick roads, there's a big (flat) one out in Redmond I accidently drove on once that someone made a nice post about https://www.dadlogic.net/old-red-brick-road-redmond/

Yeah, sometimes you see the brick where the asphalt has worn away. There's a bunch of that in Pioneer Square, I think.

I've actually been out to the Redmond brick road before (on a bicycle -- it was unpleasant).