Seattle

Seattle is a coastal seaport city in Northwestern Washington. It is the largest city in the Pacific Northwest, with over 6 hundred thousand residents.

The Son of Neptune
===Percy Jackson, Hazel Levesque and Frank Zhang visit the city during their quest to free Thanatos in Alaska. There they went to the amazon.com building headquarters in Seattle to discover the infamous Amazons to be running the company. Their leader, Hylla, turns out to be the sister of Reyna, Praetor of New Rome. This is also the place where they meet Arion. ===

The Sea of Monsters
Luke Castellan briefly mentions Seattle when conversing with Kelli, an empousa. He says that he finds it rather uncomfortable around her after what "she did to that boy in Seattle."

The Titan's Curse
Artemis casually refers to having turned a boy in Seattle into a jackelope, stating that she enjoys the practice.

The Last Olympian
Hermes confronts Percy  after the Titan War to ask him if he will make sure his other demigod children arrive safely at Camp Half-Blood. He says that there are a pair of twins in Seattle, a boy and a girl.