Portland, Oregon is an American city in Oregon on Earth, on the North American continent.
Judith Sisko, sister of Starfleet Captain Benjamin Sisko, resided in Portland. (DS9 episodes: "Past Tense, Part I", "Homefront", ST reference: The Star Trek Encyclopedia)
In 2374, Benjamin Sisko commented to Joseph Sisko that Judith was closer to their father in Portland than he was aboard Deep Space 9. Joseph retorted that the distance did not stop Jake. (DS9 novel: Hollow Men)
In 2375, Joseph travelled to Portland to tell Judith Sisko that Benjamin's mother was not Rebecca Sisko but Sarah Sisko, and that Sarah had been a vessel for the Prophets. (DS9 - Mission: Gamma novel: Lesser Evil)
Portland was the location of the home of Kieran Duffy and his family. He and his father were both buried there. (SCE eBook: Breakdowns)