A few reasons. One is there isn't much flat land; most of it is hilly and even mountainous and covered in thick forests. The flat areas are occupied with farms and towns but the space is small and not enough for big cities to grow. The hills and mountains are heavily forested and there has never been a big enough population to need to encroach on them. It's also not great for building and farming, unless grazing animals.

The other big reason is there are no natural deep sea ports in that region. It's either marshy or the estuary of the river Colombia. Small fishing towns would be fine, but not big industrial ports that drive city growth (or did in the past). Meanwhile, Portland sits further back up the river with plenty of flat land and access to the water, so makes a natural port. And Seattle sits on the bay further north and is coastal, and a good port.

The dynamic got set up of big cities further back, and those areas never really grew. Once the land became part of state forests, then that restricts growth even more.

EDIT: Here is a topographical map showing in blue the flat land: https://en-gb.topographic-map.com/world/?center=38.54817%2C-119.79492&zoom=6

What they said but also, that's the Cascadia Subduction Zone. Faced disastrous drop in land level back in the 1700s. Dunked the whole coast into the Pacific

https://en.wikipedia.org/wiki/Cascadia_subduction_zone

we just went to that area yesterday!! its very rocky and lots of cliffs on the coast, and super super hilly and forested in the interior.

many absolutely do live there, and those municipalities marked on your map there are reasonably populated. but the terrain is not super great for building large stuff, and they really do not like deforestation either. it is also farther away from freeway I-5, where most stuff on the west coast is freighted by truck, and is more expensive, at least from our experiences.

the sunset on the coast is SO pretty though :)

I was there yesterday. It's cold AF all year.

These places feel normally populated for the geography when you drive through them.

It's a Bigfoot reserve.

These are ceremonial, organ-harvesting sites.

Best to stick to the main roads.

One reason I haven't seen mentioned: it's hard to get there. The best you get is a two-lane highway (as in one lane for eastbound and one for westbound). Also because you have to go over a mountain range, there's actually very few highways to even use.

For the Oregon Coast, in that circle you have 4 highways: 6, 18, 26 and 30. If you want to go to, say, Newport you pretty much have to go to Lincoln City and then head South.

Other comments give a good tl;dw already, but in case anyone wants a video with pictures and examples, Geography By Geoff has done this topic a few times. Here's one: https://www.youtube.com/watch?v=qqyM54CNSsY

they are populated. gorgeous drive up the coast. did a week in the banana belt near the turn of the millenium. it was a very nice municipality.

Because they live somewhere else

Because somebody put a giant red fence around the area, nobody can get in.

It has been blocked off by a ring of lava

If I remember correctly, they talk about it in this YouTube video. It basically boils down to the terrain and it being bad for ports.

https://youtu.be/oojpwa5bfqg

The Goonies: am I a joke to you?

NGL I’d move to Astoria in a heartbeat if I had a remote job and a place to land lined up, but the Epstein class has decided that can’t happen

Why do you think almost no one lives there just because you don't know of a major city in the area?

It's simple logistics, there's no reason for a major city to be there.

You have Seattle, Vancouver, Victoria in the same region. And if anything is coming to the area it's going to that region already, and if it's going farther south you have better ports in Oregon.

Genuinely curious what made you interested in this idea or where it came from

Go live there yourself.

Oh, you don't want to? Why not?

There, you have your reason now.