The history of Seattle is fairly interesting for those who are not aware of it. A lot of cities have rebuilt from fires, done terraforming etc, Seattle kind of took it to a whole new level.
There's also a certain amount of "and then you're done" here.
Maybe one day we'll decide to raise Miami or New Orleans, but once all of your cities have raised themselves out of the swamps they were built on, you don't need to keep raising them for tradition's sake. You're done. And new cities, such as they are, we no longer allow to build below grade in swamps.
If you want to see something trippy, take a look at the land just west of Magnolia and Discovery Park on the King County Parcel Viewer. They were planning to fill that in back in the day and on the map you can still see all of the streets they planned and even some parcels that are still owned by people who tried to buy in early. All underwater of course.
