Plenty of them in Seattle too, I've seen them flying over downtown many times. They like to sit in the trees at Discovery Park.
It's quite convenient that the bald eagle chose the Elk enclosure as its home because that's part of the Living Northwest Trail, so it blends in seamlessly alongside all the other native, but captive, PNW animals!
The only official mention I can find of this is:
https://blog.zoo.org/2020/10/meet-raptors-superheroes-of-ski...
> Wild bald eagles often nest and raise their young in one of the trees on zoo grounds.